Hi,

I just bought a Skoda Octavia, and I stopped at a petrol station to fill her up. It just wouldn't start when I tried to leave.

I did put the right fuel in it. (if you were wondering about that)

I did get a drive home 1 day insurance which had a breakdown cover, so I was lucky enough to have the the car delivered home, 70 miles from High Wycombe to Swindon.

The guy from the recovery truck checked the fuses and he said the Engine Electronics Fuse (no.44) was blown, which is a 10Amp fuse. He tried replacing it with a 10Amp one which blew immediately. So he replaced it with a 25 amp, which started the engine for about 4 seconds, and then it blew and the engine stopped again.

Do you know what could be the problem?

Anyone of you guys heard of anything similar?

Thanks!

He put a 25 amp in place of a 10 amp :eek: What's he trying to do cause a fire :thumbdwn:

I would guess a short somewhere. Is that a fuse inside the car or on top of the battery?

He put a 25 amp in place of a 10 amp :eek: What's he trying to do cause a fire :thumbdwn:

I would guess a short somewhere. Is that a fuse inside the car or on top of the battery?

no, no, he was just trying to see if that would start the engine. He put the 10 in, and then a 15, they both blew instantly, so he tried a 25, which started the engine for 5 secs. end then just blew out.

It is a fuse inside the car.

Could it be the ECU? I just hope it's not that 'couse it would cost a lot of money to fix.

Short-circuits cause fuses to blow. A short-circuit will occur if some part of the wiring is shorted to earth by chaffing or such like, or if a component has gone 'short-circuit'.

Don't panic. Make yourself up a testing tool using a blown fuse and a low watt 12V bulb. Solder a wire on each of the bulb terminals, and connect them to each of the blades of the blown fuse. Insert the blown fuse tool into the fuse socket that keeps blowing. You now have a tool for checking the existence, or non-existence of short circuits.

Switch on the ignition and see if the bulb lights. If it lights at full brightness then you have a short-circuit. The circuit is live with ignition, and going straight to earth. The bulb lights because a circuit is complete, and any fuse you put in will blow.

If the bulb lights dimly then something in connected on the circuit and is drawing current. This will be quite normal. The best way is to isolate everything on the circuit that the fuse protects. Check the owners manual for a listing, or refer to a handbook. If everything is OK the bulb will not light.

If it does wiggle the wiring loom to see if the light goes out at any time. If it does you know you're close. It's a matter now of searching to find the fault, but it's worth knowing that these kind of faults are very often where someone has fitted something such as a mobile phone kit, fire extinguisher or audio system and inadvertently screwed through the loom or pulled on a wire somewhere.

Hope it helps a bit, and good luck.......

Hmmm, Actually the car has a Nokia cell phone kit fitted...

That is probably when they changed the 10Amp fuse with the 15Amp fuse... but now something must have gone wrong...

Thank you for the helpful advice.

Could this problem actually blow the ECU?

My nokia car kit is wired in to the loom and powers from the stereo fuse, and I did not need to uprate the fuses.

The nokia kit will have a small 2.5mm power jackplug going into the main control box - pull that out. It should also be fused with a couple of inline fuses (if fitted properly).

As we don't actually know that the problem is it is hard to say if is is likely to bloe the ECU, but I would have thought it was unlikely.

Which fuse number is it? ie. what is running on that circuit?

Sorry to mislead you.

It seems like the guy that towed the car and looked at the fuses, got the fuse assignement all wrong.

The picture from the manual was actually for a left hand drive car.

The fuse that blows is fuse number 29 - engine electronics, ignition.

And it was supposed to be a 15Amp.

Exactly opposite to it, there is another engine electronics fuse that is number 43 - engine electronics and that one is a 10Amp.

He got the 29 confused for 43. (due to both being engine electronics, and the manual being for a left hand drive car).

I don't have any fuse in socket 29 now, and the Nokia carkit still works, so it must be on another circuit, and has nothing to do with it. (i guess)

Anyway, the fuse still blows, so any advice is much appreciated.

I don't know specifically but one fuse maybe for the main relay, which provides a supply for the ECU, and one maybe for the fuel pump. Does the owners manual give any specific information, or does the fuel pump have it's own fuse that's listed as such?

You could try unplugging the ECU, and if the fuse still blows it'll prove it's not the fault. I would doubt that it is anyway. You have more than likely a wire that's chaffed to earth somewhere. From many years of experience these kind of faults may take hours to find, but only seconds to fix once you have found it.

I've just read your last post again and you say the fuse is Engine Electronics - Ignition. Try disconnecting all four ignition coils just in case one has gone short circuit, or if any of the live supply to them has chaffed on the engine somewhere. The coils will have a common supply but individually ECU switched.......

Edited 8 February, 200917 yr by Railroad

I just found out that my problem does not have anything to do with cranking the engine. The fuse blows when I simply turn the key to position 3 (the last one before engine crank).

So I don't think there is any problem with the ignition coils.

Any ideas where I should start looking for short circuits?

And the the Fault Codes are:

VAG-COM Version: Release 311.2-N

Chassis Type: 1U - Skoda Octavia

Scan: 01,02,03,08,15,17,19,35,46,56

Address 03 -------------------------------------------------------

Controller: 1C0 907 379 C

Component: ABS FRONT MK60 0103

Coding: 0004097

Shop #: WSC 31480

No fault code found.

Skipping Address 15-Airbags

Address 17 -------------------------------------------------------

Controller: 1U0 920 910 B

Component: KOMBI+WEGFAHRSP VDO V04

Coding: 03412

Shop #: WSC 25011

TMBHE41U612462128 SKZ7Z0Y0684763

2 Faults Found:

01177 - Engine Control Unit

64-10 - Not Currently Testable - Intermittent

01314 - Engine Control Module

49-10 - No Communications - Intermittent

Address 19 -------------------------------------------------------

Controller: 6N0 909 901

Component: Gateway K<->CAN 0001

Coding: 00006

Shop #: WSC 31480

1 Fault Found:

01314 - Engine Control Module

49-10 - No Communications - Intermittent

Address 46 -------------------------------------------------------

Controller: 1J0 959 799 AH

Component: 5N Zentral-SG Komf. 0001

Coding: 04097

Shop #: WSC 31480

2 Faults Found:

00953 - Interior Light Time limit

25-10 - Unknown Switch Condition - Intermittent

00943 - Heated Exterior Mirror: Driver Side (Z4)

35-00 - -

Address 56 -------------------------------------------------------

Controller: 1U0 035 161 C

Component: Radio GRO 0001

Coding: 00403

Shop #: WSC 04804

1 Fault Found:

00856 - Radio Antenna

36-00 - Open Circuit

End -------------------------------------------------------

The tool couldn't access the modules that do not appear in the log.

I just found out that my problem does not have anything to do with cranking the engine. The fuse blows when I simply turn the key to position 3 (the last one before engine crank).

So I don't think there is any problem with the ignition coils.

Any ideas where I should start looking for short circuits?

That should make the search a bit easier if the fuse blows when the ignition is switched on. You need to make yourself a tool as I described above. It won't locate your short circuit, but it will tell you if one exists or not.

Short circuits most commonly occur where the wiring loom crosses or is attached to a metal bracket or fixed onto a metal pipe or such like, or has rubbed through onto any part of the car's engine or body. The fuse blows because a wire that is live when the ignition is on is shorting directly to earth as a result of the chaffing. They can be blatantly obvious, very difficult to find, or anywhere in between.

Place the tool you made in the fuse socket, switch the ignition on and wiggle the wiring loom in various places to see if the bulb lights or goes out. If by adjusting the wiring loom you see the bulb going on and off you know you're close to finding the fault. It's a case then of looking more closely. Disconnecting any components, and/or un-taping the loom and checking anywhere that the loom might have chaffed through onto the body or engine. When the bulb no longer lights your short circuit has gone, and the fuse will not blow......

Hi all,

It happened again. I drove it 2 miles to a friend, and when I tried to start it after 30 minutes it just blew the fuse (fuse 29, 15amp). I replaced it and tried to start, it blew again.

Can anybody help me with the wiring diagrams that contain this fuse 29 (engine electronics, ignition), for my car? (Skoda Octavia Estate, year 2001, 2000cc petrol egine type AQY)

Thank you.

29 you say?? i'm on it.. i'll have a look at some wiring diagrams and get back to you

I would really much appreciate it. Thank you!

If its blowing as soon as you switch the ignition on you need to check if the fuse is ignition fed or permanent.

If its ignition fed then the short is in between the fuse box the its supply. If its permanently fed then as something is powering up its bloing the fuse (I have had several ECU's that have done this, especially after being boost started) but it could be something simple.

right i've have a look, fuse 29 should be a 15A, and it is a switched live straight off terminal 15 on the ignition switch, before the fuse it spurs off to the fuel pump relay(unfused), then after that it goes to pin 1 on he ecu, and also to the coilpack via a splice.

so i would try isolating each component in turn (coilpack and ecu) and testing for short circuits with a multimeter/continuity tester, the wire should be black with a purple tracer. it's not uncommon for a coilpack to be shorting straight to ground, i would suggest umplugging the coilpack and switching on the ignition too see if it still blows a fuse