Hi all

Right, ive started a new topic as my first topic was titled "1.6 TDI FABIA 2011 PLATE: fusebox layout and missing fuses rear wiper not working"  and no longer describes the situation I am facing.

old thread : https://www.briskoda.net/forums/topic/528866-16-tdi-fabia-2011-plate-fusebox-layout-and-missing-fuses-rear-wiper-not-working/#comment-5910143I solved the fusebox layout by reading a lot and consulting the haynes and as for the rear wiper not working, the actual fuse was in the wrong slot, maybe deliberately by the garage as I have now discovered the battery has a parasetic draw.

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I had problems with the UNI T clamp meter I had bought, subsequent testing against a brand new alternative clamp meter confirmed my UNI T was not calibrated correctly and giving me nonsense readings. I also was using an old school normal multimeter to take readings but I suspect the amp scale in it is not refined enough to help me (the mV scale seems fine though).

 

So , new thread, more educated approach. lets go.

 

From my last thread you will see that I have purchased a mk2 1.6 TDI fabia called Mavis, and the seller mentioned vaguely that the battery was flat at some point, I bought it anyway and sure enough after 3 days on the drive the battery was flat. I have since charged the battery to full and drop tested it on starting, the process for which is outlined in my last thread but simply involves watching the voltage drop across the battery terminals when cranking the engine, the battery was cranking above 10 V so its as good as can be expected. I also brought in two bigger batteries I have as slave batteries, both of these charge fine and also got drop tested and passed. I am considering purchasing a brand new battery from somewhere and taking it back when it also drains out though i kind of think this is a pointless think to do.

 

I have finally got a grip of my measuring skills and managed to establish i have a battery draw, I decided to pull fuse 50 (radio ) as this was the one that seemed to be causing problems and I then put a fully charged Numax battery in the car to measure how long in days the voltage would take to drop:

Date/Time	volts
13/01/2025 16:50	12.80
14/01/2025 20:31	12.26
15/01/2025 08:58	12.08
16/01/2025 16:50	12.02
17/01/2025 16:50	11.95
18/01/2025 16:50	11.88

 

as you can see the voltage dropped over 6 days but not by enough to cause me issues, indeed the car started fine.

 

I then took the Numax battery off and inserted a fully charged (13.43) Starline battery, putting the fuse 10 back into place and I took readings to see how the voltage dropped for the next few days.

Date/Time	Geotec meter	fall in value V
18/01/2025 16:50	13.43 v
19/01/2025 14:06	12.34 v	1.09 v
20/01/2025 16:50	12 v	0.34 v
21/01/2025 09:06	9.6 v	2.4 v

 

as you can see the fuse 50 for the radio has made the battery drain a lot quicker.

 

Using the Starline battery on the 18th I took readings for the drain when the battery was fully charged.

i have a clamp meter (new one) on the negative battery lead and it gave me a reading of 0.850 A but when placed in line on the earth side seemed to give 0.450 A either way the car was drawing power.

I then measured the voltage drop across the fuses in 3 different situations:

1..At standing, battery connected key in ignition no engine running (mV) - this is where I simply opened the car and installed the battery and took the readings. bonnet and door latches are tricked to seem closed by latching them with a screwdriver

2..With engine running (mV) - took the amp clamp off and fired up the car, again latches closed.

3..Engine off, bonnet and door latches locked and car locked, after 1 hour (mV) - I tricked all the locks and left the car for at least an hour to go to sleep before i took readings.

 

SItuation 1:

 

No.	Power consumer	Fuse rating (A)	Fuses in our box	At standing, battery connected key in ignition no engine running (mV)	Converted using fuse chart to mA
22	Operating controls for the heating, control unit for air conditioning system, parking aid, mobile phone, instrument cluster, steering angle sender, ESP, vehicle voltage control unit multifunction steering wheel	7.5 mini fuse	7.5 mini fuse	0.5 mV	46 mA
24	Central control unit of the vehicle	5 mini fuse	5 mini fuse	2.7 mV	152 mA
49	Turn signal lights, brake lights	15 big fuse	15 big fuse	0.1 mV	21 mA
50	Radio	10 big fuse	10 big fuse	3.8 mV	494 mA

 

Situation 2 & 3

No.	Power consumer	Fuse rating (A)	Fuses in our box	With engine running (mV)	Converted using fuse chart to mA	Engine off, bonnet and door latches locked and car locked, after 1 hour (mV)	Converted using fuse chart to mA
22	Operating controls for the heating, control unit for air conditioning system, parking aid, mobile phone, instrument cluster, steering angle sender, ESP, vehicle voltage control unit multifunction steering wheel	7.5 mini fuse	7.5 mini fuse	4.6 mV	424 mA	0.5	46 mA
24	Central control unit of the vehicle	5 mini fuse	5 mini fuse	3.9 mV	220 mA	2.6 mV	146 mA
49	Turn signal lights, brake lights	15 big fuse	15 big fuse	0.1 mV	21 mA	0.1 mV	21 mA
50	Radio	10 big fuse	10 big fuse	4 mV	519 mA	3.9 mV	506 mA

 

Situation 3 shows the voltage drops re appear an hour after the engines been off and are the same fuses as in situation 1.

 

So its clear from the battery depletion records that fuse 50 ( radio) is causing the biggest drain..and its clear ii its over half an amp on a 63 amph battery so its going to last 31 hours say.

 

Next step im going to take the radio out and see what happens.

Theres lots of post about Swing radios and parasitic draw, i can see the CAN is linked to the Power controller module and ive heared stuff about cutting wires etc, im just not sure if the radio staying on and drawing this power is a symptom of the CAN link not letting the radio turn off ( ignition barrel switch ?)  or is the radio itself is knackered and its the radio not letting the CAN rest... tail wagging the dog or vice versa ?

 

Its obvious to me that the last owners garage have been messing in the fuse box and may have suspected the rear wiper, hence the misplaced fuse.

 

Thoughts from others welcome .... please

 

 

 

I would say that the Canbus network is not shutting down and that of the modules remaining awake the radio is taking the most current but any one of the others is higher than what the correct quiescent consumption should be.

 

Normally the culprit is a retro-fitted Chinese head unit but this does not appear to be the case for you.

 

It could be that disconnecting the radio or any of the other modules will in itself not allow the Can network to go into sleep mode as it wont have recieved the had off signal, which is the problem with the Chinese head units, if that is the case it makes your faultfinding even more difficult, u might have to delete the radio from the Can Gateway Installation List so that it stops looking for it.

 

On my MK2 Octavia the solution to the Chinese head unit Canbus problem was to fit a Gateway controller with a later revision number.

1 hour ago, J.R. said:

I would say that the Canbus network is not shutting down and that of the modules remaining awake the radio is taking the most current but any one of the others is higher than what the correct quiescent consumption should be.

 

Normally the culprit is a retro-fitted Chinese head unit but this does not appear to be the case for you.

 

It could be that disconnecting the radio or any of the other modules will in itself not allow the Can network to go into sleep mode as it wont have recieved the had off signal, which is the problem with the Chinese head units, if that is the case it makes your faultfinding even more difficult, u might have to delete the radio from the Can Gateway Installation List so that it stops looking for it.

 

On my MK2 Octavia the solution to the Chinese head unit Canbus problem was to fit a Gateway controller with a later revision number.

Thank you J.R, for your thoughts. I have read elsewhere that the ignition key housing sends a signal to the Controller Area Network ( CAN ) once the key has been removed and that the CAN is always waiting for this signal to totally turn off the radio.

Have you heard this ?

 

additionally other people have mentioned that the CANbus network can be kept awake by other units and then this can lead to the CANbus not shutting the radio down, I dont know how much to believe this though as I doubt that just by the CANbus system being active would cause a signal to go to the radio..

 

Does my car have a gateway controller ?

I have heard of this sort of thing but I thought the factory fitted radio linked directly to the CAN network with no gateway linked in between.

I have attached a circuit diagram where I have highlighted where the power comes from the battery and into the back of the radio, also the power forks off to the Navigation System Interface (except my car does not have navigation), the navigation system interface is also controlled from the CAN by two wires which are connected to the Onboard Supply Control Unit (my car has this as its post 03/10) .  So what and where is this Gateway I wonder ?

 

Would the local dealer be able to scan the radio or the CANbus to see more info and thus diagnose whats making the CANbus stay awake ? or why its telling the radio to stay awake ?

 

Thanks in advance, Im clutching at straws a bit as I have no idea how to interrogate the CANbus system itself.

 

Circuit diagram radio highlighted areas.pdf

Sorry I dont know the answer to your questions other than thinking that to have a Canbus network there must be a master controller on my vehicle called the Canbus Gateway.

 

Once you get to this level of faultfinding it pays to purchase VCDS, with that you would see exactly what has been going on and there will probably be fault codes to guide you, paying a dealer to do this is very expensive and most will do no more than give you any fault codes shown, as a diagnostic tool it has far more capabilities than that but is only as good as the person using it who will not have the same investment in the vehicle and desire to solve the problem than you have.

Unfortunately VCDS Vag Com is extremely expensive otherwise I would consider it.

I have looked through a few posts on VCDS and its not clear whether VCDS is capable of determining the sequence/order of whats happening within the network.

As I understand it (so far) the CANbus network is a series of wires connecting various Electric control modules back to the Engine Control Unit, E.g. wiper motor has two wires running to the ECU. I have also read that the various modules only take data from the CANbus network they dont send data, now this I dont believe as otherwise how would the car know the boot was open (for example) or if the rear wiper was parked successfully (another classic battery drain issue apparently)

 

My primitive OBD scanner shows no codes (as you would expect) and I cant afford a more expensive VCDS VAg Com reader ... Im wondering if theres a secret screen on the swing radio that will tell me more info or somewhere in the system ?

 

~Hopefully someone has had this battery drain issue caused by their stereo and knows the issue better than I do. Or how to establish if just changing the radio would fix the problems, but then how do i register a new radio into the CANbus so the car knows it exists ?

 

If you remove fuse 50, then look at what is/isn't fully shutting down in test condition 3, I think you could probably blame the radio itself if everything then goes quiet.

On 24/01/2025 at 08:13, Breezy_Pete said:

If you remove fuse 50, then look at what is/isn't fully shutting down in test condition 3, I think you could probably blame the radio itself if everything then goes quiet.

 I left the battery connected last night and removed fuse 50 thinking I would start doing some testing via the OBD2 port. HAts off to you tube and this video @Ecutestinglimited

 

This is all greek to me to be honest so my first hurdle was to understand the layout of the OBD2 port, simple yeah ?

No

 

The thing is my fabia is a 61 plate so SHOULD be the one post using the K line type of "CAN" however to check I wanted to make sure i didnt stick the probes of the meter into the wrong holes and electrecute myself or the car.

So lots of places should the standard obd port layout pins 1 to 16 and what they do , however I couldnt find a specific diagram of the fabia one, not only that but every picture I viewed did not make it BLINDINGLY CLEAR if the view of the pins was from the front (drivers seat) or the back of the OBD port.

 

The image shown is as viewed from the drivers seat, and the  standard multimeter probes do not fit into the OBD2 port slots....so I gave up in frustration

 

The next day it wasnt so cold and grim and I decided to have another go by cutting off one of the legs of a crimp connector (below) and creating a homemade probe adapter, worked fantastically.

 

At this point I should say that I had unlocked the car using the fob and the battery had been connected all night with fuse 50 for the radio removed. I commenced with the tests in the video by checking the battery, 12.4 V which had dropped from the last night slightly (nothing like the normal drain I should add)

I decided that pin 16 - permanent 12 volt was the top row far left, and by testing with my multimeter from this pin to an earth point on the car body . You will see that there is a metal glint in the top row 3 left hand slots and 5 slots in the bottom row have a metal glint. So without knowing I could have assumed pin 1 was pin 16 given I was unsure of the pin layout to start with...which I duly did and of course pin 1 carried 12 V !!!  At this point I decided to turn the ignition key off, something which I was unclear about initially despite my youtube cruising. When I retested with the ignition off I found that the top left slot as viewed above carried 12.4 V

 

Can anyone confirm that pin 16 is as I describe when viewed from the drivers seat ?

 

Onto the tests:

Test 1 - battery check was a pass. 12.4 V

Test 2 is the canbus asleep ? - I took a reading between the (assumed) pins 6 and 14 and got 0 V , so my canbus was asleep, though I question this as my clamp meter (on battery negative wire) was giving readings which suggested otherwise.

Test 3 resistance check between pin 6 and 14, there was no open circuit and the reading was 66.4 Ohms, slightly higher than the 60 Ohms in the video but not lower than 60 ohmsor bang on 120 ohms which would have indicated other issues (see the video), rather I am taking my slightly high reading to show resistance caused by poor connections.

Test 5 - not required

Test 6..(yes its out of turn I know) Short to ground and short to voltage - checking for continuity between pin 4 (chassis ground-i hope) and pin 6 and then pin 4 and pin 14 gave me a reading of 0 and no signal from the continuity buzzer, so all good there. Then checking for voltage between pin 4 and pins 6 and then 14 gave me a voltage reading of 2.52 V, which apparently shows there is a "short to voltage" according to the video I watched that is were the voltage line of the CAN is shorting to the other line of the CAN. So I am thinking that short could be at the plug on the radio or (worse) somewhere else in the entire CANbus network and that this short is keeping the radio powered up, that said apparently according to test 2 my CANbus net is asleep.

 

Test 4.. Remove the suspect equipment (radio) and do a resistance check from the CANbus wires that connect to that module..and once again here I am struggling, several of the wires that go into the terminal plug on the back of the stereo are twisted together, which is how the CAN hi and low cables were described to be. Also I need to test from the front of this plug as I dont want to try ramming things into the back.

 

Tomorrow I shall go back to it, locate the right pins for can hi and low in the radio plug and do a resistance check backwards to the CANbus network. Hopefully I will get the 66.4 Ohm reading or indeed a 60 Ohm reading and I will know the wiring is sound and it must therefore be the radio itself. I am not sure however if by removing the radio I will cause the rest of the CANbus to keep "hunting" for the radio module ? I have read somewhere ab out people having to de-registger their radios with the car "brain" and re-register new ones when they do swap outs etc.

 

Really I need to know for sure what the slot numbers are as viewed from the front of the OBD2 port, and what they do, if I am right then my OBD2 port has connectors for the ISO9141 L line at pin15 and the ISO9141 K line at pin 7 , which I did not think it would have as its post 2010 and should be ISO 15765-4

 spec.

I should be able to marry up the cable colours from the circuit diagram in the haynes manual to the ones I can see in the back of the radio plug and work out the CAN hi lo wires.

 

So thats it for today. Im sick to the back teeth of clever cars, my reliant rebel does not have these issues

 

Any thoughts on the above would be helpful please, I know is a long read and I have some more tests from the video to do but Rome was not built in a day.

I would like to fit a bluetooth streaming radio into the car, but I dont want anything that will cause CANbus issues (which I believe the Amundsen will do ) so Im thinkng the bluetooth swing radio which is from the rapid will be good for me  (i believe) anyone know if this is a straightforward mither free and future proof swap please ?

 

thanks for any advice peeps

Dabber

 

Edited 25 January, 20251 yr by Dabber2024

Sorry, I didn't make myself completely clear, I think.

I wasn't suggesting direct attempts to probe the comms.

What I meant was, remove fuse 50, do all the stuff to make the car think it is all closed up, wait at least 30 minutes after, then repeat your mV across fuses measurements. 

If those that showed activity before now don't,  you can probably conclude that in the absence of the radio, everything else shuts down properly. 

You have identified pin 16 correctly on the diagnostic socket, by the way. You can see that only 8 of the orifices have contacts in,

 

pin 1 bottom right in your pic - ignition switched 12V

pins 4 and 5, leftwards from there, 0V/earths

pin 6, CANH

pin 7, K line

pin 14, CANL

pin 15, L line to airbag control unit

pin 16, permanent 12V

 

I may watch your video later if I find somewhere with better internet.

1 hour ago, Breezy_Pete said:

You have identified pin 16 correctly on the diagnostic socket, by the way. You can see that only 8 of the orifices have contacts in,

 

pin 1 bottom right in your pic - ignition switched 12V

pins 4 and 5, leftwards from there, 0V/earths

pin 6, CANH

pin 7, K line

pin 14, CANL

pin 15, L line to airbag control unit

pin 16, permanent 12V

 

I may watch your video later if I find somewhere with better internet.

Thank you Pete. I shall sketch out your info on a diagram for future people to peruse.

I will do as you suggest on fuse 50. But first I will run the tests now the cars sat with the radio out overnight as thats almost the same.

Right, quick addition.

Went to the car yesterday and the battery was down to 9.9 V, which was slightly  more declined than I was expecting but as the cars still draining power not a surprise. The car was opened with the fob, then the door locks tricked and the bonnet lock tricked.The radio has been removed for 2 days or so now.

 

I repeated

Test 2 is the canbus asleep ? - Result was no current between Pin 6 & Pin 14. I had assumed that by opening the car doors I would have triggered the CANbus awake , but it seems not. Would be interested in views on what actions are needed to wake up the CANbus ?

 

I then performed

Test 6.. Short to ground and short to voltage - the results were the same as before, no continuity but a voltage reading of 2.52 V. So the voltage line of the CAN is shorting to the other line of the CAN (im not sure im correct in suggesting only one line of the CANbus net carries voltage as I believe the system works on voltage differential between the lines ?) Regardless its still a short.

 

I suspected a short in the radio or the radio Quadlock connector, so I then performed.

Test 4.. Remove the suspect equipment (radio) and do a resistance check from the CANbus wires that connect to that module..I studied my Block A multiplug and worked out the pins to check from the front of the BLACK plug block, used my homemade crimp attachments to check resistance between the wires - the reading was OL (NO RESISTANCE). which is BAD. The testing video I watched tells me that I should have been getting the 66.4 Ohms I had at the OBD2 connector if the Loom is OK . So it seems there is a break in the CANbus Loom somewhere. This is consistent with the indication in test 4 of the short to voltage. So my radio unit is probably OK.

Terminal pin	BLOCK A	My wiring colours	What haynes says	Correct or wrong ?
9	CAN bus, high	green/orange	OG/GN	CORRECT
10	CAN bus, low	brown/orange	OG/BN	CORRECT

 

At this point I performed a continuity check on the pins within the plug block, 9 and 10,  from the front of the pin to the back of the pin, they are good with continuity.

 

So now I need to work out what units make up the CAN bus and where on earth the CANbus wiring runs in the car 😞 

I need a map of the CANbus as it sits within the car - if such a thing exists , i cant find one yet.

 

I replaced the battery with a fully charged one and closed up for the night.

 

Today I shall go back down and start the car etc to try to wake the CANbus up, im not sure why I don't get voltage showing the can being awake when I would have thought it should be ?

After that I shall trick the locks again and wait half an hour and do as Pete suggests and measure the voltage drops as I didn't want to do that with a low battery in place.

 

If anyone can supply a CANbus map that would be very helpful.

 

Dabber

 

 

 

 

SKODA Fabia, Diesel 1.6 Registered Sept 2011.Elegance.

 

Swing Radio

 

 

 

 

Checking on my quadlock multiplug A connector indicates that my Rear and Front LH and RH speakers have been wired in reverse (my fabia was built in Spain BTW) See table below, Pin 1 & 4 for example in my car the Red Green wire on pin 4 should really be on pin 1 according to Haynes Manual. I have colour coded the speakers in the table so you can see which ones have been wired in reverse.

 

I have not tried using the Fade left and right of the stereo to confirm this as the only DEFINITE way to know which wire goes to which speaker is to check at the door hinge or at the speaker. It may be that I can run a test current down the speaker wires individually and see if the speaker makes a noise, this would be better than ripping the doors open to get to the speakers (sigh).

 

Terminal pin	BLOCK A	My wiring colours	What Haynes Manual says	Correct or wrong ?
1	Rear right loudspeaker, positive	Blue/White	RD/GN	WRONG
2	Front right loudspeaker, positive	BLUE	RD	WRONG
3	Front left loudspeaker, positive	RED	BU	WRONG
4	Rear left loudspeaker, positive	Red/Green	BU/WH	WRONG
5	Rear right loudspeaker, negative	Brown/White	BN/GN	WRONG
6	Front right loudspeaker, negative	Brown/Blue	BN/RD	WRONG
7	Front left loudspeaker, negative	Brown/Red	BN/BU	WRONG
8	Rear left loudspeaker, negative	Brown/Green	BR/WH	WRONG
9	CAN bus, high	green/orange	OG/GN	CORRECT
10	CAN bus, low	brown/orange	OG/BN	CORRECT
11	Display voltage supply, positive, optional only on the Low radio version
12	Voltage supply, negative, terminal 31	Brown/Yellow	BN/YE	CORRECT
13	Display HS CAN bus low, optional only on the Low radio version, not for Midline
14	Display HS CAN bus high, optional only on the Low radio version, not for Midline
15	Voltage supply, positive, terminal 30	2 off Red wires	RD	CORRECT
16	Anti-theft coding control signal, SAFE, positive	Single Red	RD	CORRECT

 

 

 

 

FAbia RAdio plug wiring pdf version.pdf

Edited 29 January, 20251 yr by Dabber2024

Hello all

Back to it today and starting from the top with a fresh battery. Firstly i need to answer @Breezy_Pete

I tricked the car locks and left the car for 30 mins or so and took readings across the fuses as you suggest. fuse 24 was giving a reading of 3.5 mV, this is the central control unit fuse. fuse 22 was also giving a voltage of 0.5 mV this is the voltage control unit fuse amongst other things. Fuse 50 (radio) was no longer giving a reading, the radio was not fitted for this test. The battery was still depleting but at a much slower rate as previously mentioned in my posts.

So it seems the radio is not the only source of the drain.

 

I next went through the tests from the video but jigged the order, first i left the battery negative cable off, then i attached the battery neg cable but left the ignition key out of the barrel, then I did the tests again with the ignition on. The results are tabulated below.

The first thing i noticed was that the 66.6 Ohm reading between can hi and lo at the obd2 port was not repeated at the radio multiplug which I have a feeling it should have been

The next thing I noticed was the constant voltage of 2.51 V on both can hi and lo at the obd2 port with the battery connected, my understanding was that can hi should have read 2.58 ish V with Can lo reading 2.4 ish V.

 

Im not sure what to make of all this other than, the main spine of the canbus is intact, the radio spur from the canbus gave a reading of O.L which is wrong. So my thinking is the canbus leads from the radio are broken prior to joining the loom. I also think there is a voltage short present somewhere, maybe at the same point.

 

 

Test number	Test purpose	Notes	Result	Further questions
Test 1	Establish battery voltage	Fresh fully charged	12.9 V
Test 2 Ignition off battery not connected	Is the CAN network asleep. At the OBD2 port.	Check voltage between AN hi and CAN low pins 6 and 14 on the latest CAN design (post a2008 ? ).Reading should be 0 V if network is asleep	0 V	No battery connected..no power anywhere
Test 3 Ignition off battery not connected	Resistance check of the network at the OBD2 port and the terminating resistors. Test between CAN hi and CAN low	There are two resistors built into the two modules at the two ends of the network, they are 120 Ohms each. Measure resistance between pins CAN hi and CAN low pins 6 and 14 should be 60 Ohms	66.6 Ohms	So the main spine of the CANbus is in one piece
	If you get a GOOD 60 Omh reading	It could still be a module has a break in one of its CAN wires, providing the module is Not a gateway module OR it doesn’t contain a terminating resistor
	Resistance check of the network at the radio multiplug can hi and lo. Test between CAN hi and CAN low	Measure resistance between pins 9 CAN hi and 10 CAN low,	0.1 Ohms	Given the main spine is reading 66.5 Ohms I was expecting to read that at the radio plug, am I correct in this presumption ? From the video notes they say, providing the radio is NOT a gateway module or has no terminating resistor then this test when performed at the OBD2 port would indicate a possible break in the Radio CAN wire or other module
Test 4 Ignition off battery not connected	Short to ground at the OBD2 port– You cant test resistance with current flowing	Set to Continuity and check between Chassis Ground (pin 4) and CAN hi and low. If ANY CONTINUITY IS DISPLAYED THEN THERE IS A SHORT TO EARTH ON the circuit somewhere. If YOU GET 60 Ohms on both CAN hi and CAN low then thats good	Pin 6 CAN Hi 14.41 kOhms Pin 14 CAN low 14.41 kOhms
	Short to ground at the Radio multiplug CAN hi lo	Set to Continuity and check between pin 9 & earth and pin 10 & earth, Pin 12 used as earth	Pin 9 CAN Hi 3.64 MOhms Pin 10 CAN low 5.8 MOhms	Value kept climbing on the scale , no continuity beep
Test 5 ignition off, battery connected	Check voltage at the OBD2 port	Set to DC Volts and check between Chassis Ground (pin 4) and Pin 16 power, should get the battery voltage reading	12.9 V
Test 6 ignition off, battery connected	Is the CAN network asleep. At the OBD2 port.	Check voltage between AN hi and CAN low pins 6 and 14 on the latest CAN design (post a2008 ? ).Reading should be 0 V if network is asleep	1 mV	How can the meter measure voltage BETWEEN the two can hi and lo pins ? They both carry voltage normally when awake and to measure the voltage the electricity has to flow to earth doesn’t it ?
	Is the CAN network asleep At the radio mujltiplug.	Check voltage between pin 9 can hi and pin 10 can low	3.5 to 4.9 V	Value was fluctuating
Test 7 ignition off, battery connected	Check voltage at the OBD2 port	Set to DC Volts and check between Chassis Ground (pin 4) and Pin 16 power, should get the battery voltage reading	12.88 V
Test 8 ignition off, battery connected	Short to voltage at the OBD2 port	Set to DC Volts and check between Chassis Ground (pin 4) and CAN hi and low. No voltage should be displayed if the BUS is asleep. If you get voltage then theres a short to voltage somewhere	Pin 6 CAN Hi 2.51 V Pin 14 CAN low 2.51 V	Static value no fluctuation.
	Short to voltage at radio multiplug can hi lo	Set to DC Volts and check between CAN hi pin 9 & earth and CAN low pin 10 & earth.	Pin 9 CAN Hi 0.59 V to 0.8 V Pin 10 CAN low 4.3 V to 4.9 V	Value was fluctuating
	Short to ground at the OBD2 port– You cant test resistance with current flowing but tried it anyway	Set to Continuity and check between Chassis Ground (pin 4) and CAN hi and low. If ANY CONTINUITY IS DISPLAYED THEN THERE IS A SHORT TO EARTH ON the circuit somewhere. If YOU GET 60 Ohms on both CAN hi and CAN low then thats good	Pin 6 CAN Hi O.L no buzzer sound Pin 14 CAN low O.L no buzzer sound
	Short to ground at the Radio multiplug CAN hi lo	Set to Continuity and check between pin 9 & earth and pin 10 & earth, Pin 12 used as earth	Pin 9 CAN Hi O.L no buzzer sound Pin 10 CAN low O.L no buzzer sound
Test 9 ignition ON, battery connected	Is the CAN network asleep. At the OBD2 port.	Check voltage between AN hi and CAN low pins 6 and 14 on the latest CAN design (post a2008 ? ).Reading should be 0 V if network is asleep	0.9 mV	How can the meter measure voltage BETWEEN the two can hi and lo pins ? They both carry voltage normally when awake and to measure the voltage the electricity has to flow to earth doesn’t it ? In this test obviously there is no battery connected but later
	Is the CAN network asleep At the radio mujltiplug.	Check voltage between pin 9 can hi and pin 10 can low	3.49 V to 3.52 V	Value was fluctuating
Test 10 ignition ON, battery connected	Check voltage at the OBD2 port	Set to DC Volts and check between Chassis Ground (pin 4) and Pin 16 power, should get the battery voltage reading	12.53 V
	Short to voltage at the OBD2 port	Set to DC Volts and check between Chassis Ground (pin 4) and CAN hi and low. No voltage should be displayed if the BUS is asleep. If you get voltage then theres a short to voltage somewhere	Pin 6 CAN Hi 2.53 V Pin 14 CAN low 2.53 V	Static value no fluctuation.
	Short to voltage at radio multiplug can hi lo	Set to DC Volts and check between CAN hi pin 9 & earth and CAN low pin 10 & earth. Pin 12 used as earth	Pin 9 CAN Hi 0.71 V to 0.75 V Pin 10 CAN low 4.27 V to 4.23 V	Value was fluctuating

Any thoughts on the above post would be welcome, tomorrow I shall start stripping back the can bus wires from the radio as I believe the ground short is causing other modules like the Voltage control unit to misfire and stay awake, in turn this is keeping the radio on which enhances the battery drain.

I still really need a diagram of the canbus network and the points at which I can split the loom to test the separate parts.

I found this which is maybe for an octavia.

ive also just found this:

 

on another source.

10 hours ago, Dabber2024 said:

Any thoughts on the above post would be welcome, tomorrow I shall start stripping back the can bus wires from the radio as I believe the ground short is causing other modules like the Voltage control unit to misfire and stay awake, in turn this is keeping the radio on which enhances the battery drain.

I still really need a diagram of the canbus network...

PM'ing you about this now.

7 hours ago, Breezy_Pete said:

PM'ing you about this now.

Cant thank you enough Pete, im going to look at that now.

For anyone interested heres a link to a site with lots of workshop manuals and diagrams on every VW group car out there !

https://www.vag-hub.com/fabia/fabia-mk2/

 

Small update on the radio parasetic drain.

Based on my belief that there is a short to ground on the radio canbus somewhere i took a look at the radio wires, they were fitted badly and part of the loom where it disappears to the right of the radio was slightly damaged. One of the black radio aerial wires was showing bare silver wire and also the earth wire (brown/yellow) that terminates in pin 12 ( Voltage supply, negative, terminal 31)

 

So i taped these up in the vain hope this might be the cause of  a short.

It didnt seem to be, i refitted the stereo and after 30 mins tested the current drain again and the radios still pulling voltage.

Ref Pete i felt along the loom and can feel the bulge where the radio wires join the main loom, can see it of course 😞 still good to know where it is.

 

Before I get to removing the dash I am wondering if it is some other module thats giving the whole system the yips as it were and Ive come across videos of similar battery drains being caused by the alarm horn.

Interestingly on the times that I have been testing the car I have had the door and bonnet locks tricked waiting for the CANbus to go to sleep and when I opened the door to get in the indicators all started to flash, BUT no horn sound !

so Im now wondering if the alarm horn is up to no good, thanks to some advice I can see the Horn for the alarm is not on either the CAN line however hmmmmm.

 

My mate has a mate in Northwich who is a auto tech and we shall take the car to him one saturday to see if he has a tool that can run a diagnostic and show the topology map of the CAN bus lines, if he has all the gear then that night rule out the radio, though the short to ground is still there, im going to check that tomorrow when I switch batteries I think ,make sure I wasnt seeing things.

 

Dabber

 

I think you have convinced yourself that there is a short to ground on the can line and are chasing a phantom, the voltages at the OBDII port look correct to me for when no data transmission is taking place.

 

You should disconnect the alarm horn, it isn't doing anything by the sounds of things, and see if the parasitic discharge is removed.

 

I thought the alarm module was a Can node, it certainly brings up a no comms fault code when it is removed. I'm pretty sure that it is on the installation list.

Edited 10 February, 20251 yr by J.R.

11 minutes ago, J.R. said:

I think you have convinced yourself that there is a short to ground on the can line and are chasing a phantom, the voltages at the OBDII port look correct to me for when no data transmission is taking place.

Well J.R., i need to find a reason as to why the battery drains 3.5 V over 4 days , theres nothing ghostly about that.

 

It may be that the fault does not lie in the CANbus but as per the table below from right at the start the values for power draw are above normal (quiescent ? )

 

Situation 2 & 3

No.	Power consumer	Fuse rating (A)	Fuses in our box	With engine running (mV)	Converted using fuse chart to mA	Engine off, bonnet and door latches locked and car locked, after 1 hour (mV)	Converted using fuse chart to mA
22	Operating controls for the heating, control unit for air conditioning system, parking aid, mobile phone, instrument cluster, steering angle sender, ESP, vehicle voltage control unit multifunction steering wheel	7.5 mini fuse	7.5 mini fuse	4.6 mV	424 mA	0.5	46 mA
24	Central control unit of the vehicle	5 mini fuse	5 mini fuse	3.9 mV	220 mA	2.6 mV	146 mA
49	Turn signal lights, brake lights	15 big fuse	15 big fuse	0.1 mV	21 mA	0.1 mV	21 mA
50	Radio	10 big fuse	10 big fuse	4 mV	519 mA	3.9 mV	506 mA

 

Some more study on you tube diagnoses the curious equal voltage values on can hi and low of 2.51 V in my test 8, they were static values on the meter with no fluctuation, as described at 15:00:00 in this video
https://youtu.be/JicbzR3Juh0?feature=shared 

this might indicate can hi and low are shorted together, so Mr Diagnostek says to perform a resistance test between can hi and low at the OBD, in his video he gets a 0.2 Ohm  resistance instead of 60 ish Ohm and hes suggesting that means the can bus wires are shorted together rather than to ground as he also had equal static voltage values. In my readings my OBD can hi and low resistance check gave me a good 60 ish ohm reading BUT my resistance check at the RADIO plug gave me a 0.1 Ohm when really it should have been 60 ish ohm (according to the other video https://youtu.be/fZMNzKpCGfc?feature=shared here.)

 

I shall research alarm horn issue and also remove the J519 module as I might be able to at least split the two CANbus systems and determine something more.

Ultimately I have to fix this car otherwise my wife will get anxious driving it and I am not having that, perhaps this level of diagnostics is a bit much for an amateur but the battle is far from over - cue bugles and the sound of the Light Brigade  

 

 

 

 

 

 

 

Alarm horn on your car appears to be fused from Fuse 54, 15 Amp value. It has only LIN 1-wire comms to the BCM, not CAN connected. See if there is evidence of a drain via that fuse? (Not mentioned in your original post, so I guess not?)

 

Would be good to get a VCDS scan of the BCM (module 09) to see if it is registering a fault with the alarm horn (probably). That may, I suppose be causing things to not shut down fully. Not sure.

 

 

Edited 11 February, 20251 yr by Breezy_Pete

A VCDS scan will also reveal if there is a Can fault.

 

I doubt that the vehicle systems would continue to run with a dead short between CanH and CanL, I believe it can run in a restricted single wire mode if one conductor is open circuit but a dead short?

 

Looking at the diagram for the Octavia the Can gateway module has 5 different CAN network ports, one being for infotainment, if you are sure that you probed the correct terminals when you got the 0.1 ohm reading then you should remove the connector from the Gateway controller, find the wires to the radio (they will have a distinct colour code) and see if you get the same reading there, if you do then you have to identify and remove any other modules on that network and if the short remains the start inspecting the cabling throughout its length.

 

VCDS would make all of this so much easier or maybe instantly disabuse you of your notion saving a lot of time and headache.

 

Does the radio work?

 

Does it react to info from the infotainment Can network? I dont know what your radio does but at the minimum it would be illuminating the display when lights are on, other features (according to radio level) would be displaying doors open, volume increasing with speed etc.

@Breezy_Pete

@J.R.

Comments noted and will check the alarm fuse. The radio does indeed work, and I am looking at getting a vagcom connector and downloading VBCDS-lite

 

Update:

Following from my previous entries I am pursuing the course of least resistance and have now re-routed the 12V power to the radio from its original fuse (50) and have taken a power lead from fuse 1 (micro fuse) bus rail, which is switched. So now at least I dont have to keep whipping the fuse in and out.

Next I took a look under the front scuttle for the alarm siren horn.....guess what....no alarm siren present, the wire and connector plug was lying loose in the scuttle but the horn has been removed, looks like someone mangled the bracket slightly as well. See attached.

I stated on https://www.briskoda.net/forums/topic/525881-alarm-interior-sensor-shut-off-switch/ this post that my drivers door indicator light was also showing an error somewhere in the central locking ref the flashing sequence of the little red light at the top of the drivers door card.

 

So my thoughts are now running to there being a central locking issue, triggering the alarm all the time, so someones removed the alarm, and now my battery drains and the central locking is not always working right.

 

So 1st this means I need to buy the alarm siren, which means the right part number , my best guess so far is  1K0 951 605 C for the part number based on looking for internet sales for fabias from 2011. 

 

I could do with this confirming however if anyone happens to know the correct part number for a skoda alarm siren ?

 

Thanks

Dabber

 

4 hours ago, Dabber2024 said:

I could do with this confirming however if anyone happens to know the correct part number for a skoda alarm siren ?

For your car, the catalogue says 1K8951605B, [my emphasis on the 8] which has been superseded by 1K0951605F  the latter retails at £207.50 + VAT currently in UK.

 

5 hours ago, Dabber2024 said:

So my thoughts are now running to there being a central locking issue, triggering the alarm all the time, so someones removed the alarm, and now my battery drains and the central locking is not always working right.

 

Your logic sends you down expensive rabbit holes. You seem to be overlooking the basics and diving deep into complicated stuff requiring a lot of study

 

Octavias will work perfectly without the alarm siren I see no reason why yours should be different.

 

On 10/02/2025 at 20:18, Dabber2024 said:

interestingly on the times that I have been testing the car I have had the door and bonnet locks tricked waiting for the CANbus to go to sleep and when I opened the door to get in the indicators all started to flash, BUT no horn sound !

 

On a very basic level this says something very important, the door closed switch is either not working or signals from its controller confirming it being closed are not being received by others allowing the system to prepare to enter shut down mode.

 

2 very common basic faults, 1 the door lock microswitch for the former. 2 damaged wiring in the door bellows for the second.

 

Have you checked either of them?

 

You now know why the horn was not sounding but the indicators flashing.

 

Edited. I take the above back, you "tricked" the door closed microswitch then opened the door without releasing it, I can't get my head around quite what the electronics thought were going on.

 

I really think now is the time to invest in VCDS, its reminding me of when I was forced (through my own stubbornness) to scrap my MK1 Octavia only to have to buy VCDS for the MK2 and then realise that with it I would not have had to scrap the MK1.

Edited 28 February, 20251 yr by J.R.

@JR RS  Judging by the dash display the door close and open switch is working, thats not to say it doesnt need cleaning at the least though, which I will do. Octavias might work without an alarm siren but I would like to have a working car alarm on my fabia and from the many other fabia posts and sites I have studied the dodgy alarm battery or link does cause a battery drain, possibly through the 3rd control wire in the connector plug. At present my time only allows for brief periods of work so  no taking of the door to pieces yet. I will check the door bellows next all round the car. I am working on installing VCDS lite just need a microsoft PC first and apparently a cable (usb to OBD2) not all cables work though so need to get one that reads the K line it seems.

 

@Breezy_Pete Thanks for the part number, I will be looking at sourcing one asap, there are options from Ali express i believe but to be honest my local scrap yard will be the first place to go I think to get OEM, then perform a battery replacement on the part if required. I am hoping to find a 1K0951605F on a newly scrapped recent model if it is now the VW go to part number, maybe its on the new octavias ? who knows.

 

Fix alarm horn first

Investigate bellows

Check for parasetic draw again

 

Arrange day to take door to pieces and look at the microswitch possible open the controller module to check the solder connections as there is an interesting post around the earth causing trouble regarding the interior door alarm sensor disable button. From the research done so far the interior sensor deactivation button should be lit red then turn orange when pressed to indicate it is in action. I might visit the skoda garage to see another fabia in action.

 

Dabber