My new vehicle has stored fault codes P0671/2/3/4 for all 4 glowplugs, erased and did not return until staring in colder weather this week, each time its all 4 injector codes coming up. I have removed the harness and all 4 connectors are clean, shiny and grip tightly, used switch cleaner just in case and codes still come back after each cold restart.

 

Its  4 wire harness and logic tells me that for all 4 to show the fault each time its a high resistance in either the relay contact, suppy fuse, any downstream connector or perhaps the engine earthing, the Haynes manual for this vehicle is pretty useless for wiring diagrams compared to the one for the previous MK1 Octavia, there is no diagram for this system.

 

Is there anywhere I can find a diagram for this system so I know where to look and test for high resistance contacts? Failing that can someone tell me where to find the glowplug relay, which fuse carries the glowplug current, whether there is any connector between it and the engine, whether there is a seperate engine earth for the cylinder head injectors and glowplugs?

 

Many thanks in advance, I dont want to be stripping out and splicing in a loom if its not needed, the fault codes are not bringing up any awrning lights and it seems the glowplugs are doong their job but until the really cold weather arrives I cant be certain.

What year was the car built?

For glow plug testing it is useful to know that if you unplug the coolant temp sensor the ECU gives the max glow plug time which maybe 20 or 30 seconds.

 

This gives you enough time to check the harness to see if you have power to any of the cylinders. If you do this simple check first and you don't have anything you can start digging further or replace the glow plugs if necessary.

 

You haven't mentioned how old the car is and when you last changed the glow plugs, they don't last forever.

Edited 30 September, 20187 yr by SuperbTWM

Vehicle is 2006.

 

I dont need to do a simple check to see whether I have power to the glowplugs or to test them, they are operating and I can also see that from the volt drop.

 

The engine controller is seeing a glowplug voltage out of limits, probably too high because of a resistance that is common to all 4 plugs, I need advice as to where to find the probable points where contacts could become oxidised, the relay, the fuse, any upstream connector or downstream earth.

 

I have not replaced the glowplugs and have no intention of doing so unless one fails, and they will not all fail together, my last Octavia did 325000 miles on the original glowplugs.

Edited 30 September, 20187 yr by J.R.

Should be fuse 27 in the E-box, powering the automatic glow plug period control unit "below the E-box" as far as I can see. 

E box, is that the one by the battery?

 

The fuse that powers the relay is probably not the one that carries the glowplug current that is switched by the relay, if I could see a wiring diagram all would be revealed, the ones in my Haynes manual for the MK1 were very usefull but for the MK2 they are a chocolate teapot, yet again they have decided in their wisdom that its something beyond the capabilities of owners.

Edited 30 September, 20187 yr by J.R.

 

32 minutes ago, J.R. said:

Vehicle is 2006.

 

I dont need to do a simple check to see whether I have power to the glowplugs or to test them, they are operating and I can also see that from the volt drop.

 

The engine controller is seeing a glowplug voltage out of limits, probably too high because of a resistance that is common to all 4 plugs, I need advice as to where to find the probable points where contacts could become oxidised, the relay, the fuse, any upstream connector or downstream earth.

 

I have not replaced the glowplugs and have no intention of doing so unless one fails, and they will not all fail together, my last Octavia did 325000 miles on the original glowplugs.

 

It would of helped if you had included this in your first post but no problem. And no the glow plugs don't all fail together but by the time some people get to see the codes often all 4 have failed due to them not bring up an EML.

 

 

OK I will check the volt drop again tomorrow and if need be their resistance, all 4 failed could be a possibility but my luck is always good!

 

Its not really cold enough yet to  know 100% that they are working, could be yet another reason why the previous owner decided to sell the vehicle, winter starting in previous years and a pricey quote from their garage.

I'm not questioning your methods, you have had a very logical approach to the problem and it does sound like you have a common issue, but I personally still like to make sure the basics are fine before wasting time digging into a problem that isn't really there.

 

I've replaced a few sets of glow plugs on cars I've had that have been around 100K or less and I've never found any that have been working properly IE glows in the same proportions to a new one in the same amount of time. Don't forget even in fair weather when the glow plugs do not fire up pre start, they do come on post starting for some time so they get a lot of use.

 

Good luck!

 

 

Unless the car becomes difficult to start I wouldn't go looking for problems to fix.

 

Just because a scan shows something doesn't mean it's mission critical.

 

Take a step back and relax.

9 hours ago, J.R. said:

E box, is that the one by the battery?

 

The fuse that powers the relay is probably not the one that carries the glowplug current that is switched by the relay, if I could see a wiring diagram all would be revealed, the ones in my Haynes manual for the MK1 were very usefull but for the MK2 they are a chocolate teapot, yet again they have decided in their wisdom that its something beyond the capabilities of owners.

 

I dunno where the ebox is, just going by wiring diagram info which you can download yourself for a modest fee at erWin Skoda.

The fuse I suggested checking is indeed the one that feeds high current to the relay, thereby the glowplugs. 50A rated IIRC from last night.

Thanks for all the replys, I will purchase the wiring diagrams from the site you recommend.

 

I dont worry about faults and before discovering VCDS would often put up with them or work around them for a long time while working out what the actual cause was, sometimes other things would manifest that would lead me to the solution, I like to work that way.

 

but now i am having to adapt because the power of VCDS gives me info that I would never have been aware of, also while learning how to use it its usefull to be tracking this particular fault, I resolved the airbag fault which has plagued the car for 10 years and cost previous owners over a thousand pounds cumulatively by my own logic and deduction, VCDS was a good aid though.

 

When i get a new S/H vehicle i like to try and resolve as many existing faults as possible before letting the new ones build up, I am not at all concerned with the glowplug fault codes but it would be nice to resolve, the high resistance may eventually become bad enough for me to have noticed anyway. There is another code that comes back as soon as its removed saying that my instrument binnacle is faulty, it works perfectly and I have done all the output tests to double check, its just one of those things that I may eventually decide the glowplug codes are as well.

 

In the meantime its fun to discover a completely new way of diagnosing problems and to realise why so many modern mechanics dont develop the analytical skills that my generation did, they would replace all 4 glowplugs, then when the codes remained, the harness, then the relay etc and never have concluded that it is one common fault or even no fault at all, just the volt drop parameters being to narrow.

3 minutes ago, J.R. said:

I will purchase the wiring diagrams from the site you recommend.

 

Good plan, there are 6 different options for Octy 2 circuit diagrams by date, I found the latest version to feature the BKC engine was the one dated October 2005, so that's where the quoted info came from. You could just download them all though, they're variable from several hundred to a few thousand pages long, so ctrl-F is highly recommended for navigating around within them. 

Have a good browse around the site, particularly the Repair information and Training items sections under the Individual vehicle information tab, once you've registered and logged in, but prior to paying for your hour's access, in order to maximise your use of the time to get everything interesting/relevant.

 

 

That is timely, I just registered and was having a look, it all looked quite intimidating and I had no idea which was the correct wiring diagram or what it contained, "basic equipment" suggested to me that it was just the chocolate teapot as in the Haynes manual, is it a full wiring diagram for the whole electrical system?

 

good advice about the browsing, I found it quite hard to find any info but will try harder, forgive my ignorance but what does CTRL-F do? make a note of the bits you want to download?

 

A work break beckons now so will look again later

Ctrl-F finds things within big documents once you've downloaded them, e.g. "BKC".

They are indeed full wiring diagrams, there is a knack to working with them - wires ending in a rectangular box with a number inside continue at the numbered current track.

Current track numbers are what run along the bottom of each diagram.

Thats excellent! Thanks again!

 

I am used to working with current flow diagrams spread over several pages, the first big evolution for me was a complete rewire of a 1995 Galaxy, took some getting used to but they are far better, a bit like reading an OS map, there is so much info there that initially you are not aware of.

 

€7 or perhaps it was $s is a small price to pay and to have some of the self study programs, I already found and printed off one on the 1.9 litre PD engine, an excellent resource for someone with a thirst for knowledge.

Edited 1 October, 20187 yr by J.R.

Ok so I have browsed and made a list, I feel like a kid locked in a sweet shop, what a find

 

Do they take a long time to download? Stupid question as it will depend on the computer, mines a 7 year old laptop, I have chosen 5 manuals and wiring diagram and 12 self study guides, will I need to prioritise them or could they all be downloaded in an hour?

 

Remains to be seen if my computer is fast enough and has enough space.

 

Thanks again for the heads up of the site, knowledge is everything and by studying and learning all this I know that I will be able to continue vehicle maintenance for another decade, longer still if I dont buy anything newer.

 

If I had VCDS before and perhaps some of the knowledge from the study guides I would not have needed to scrap my MK1 Octavia but the MK2 that i got for next to nothing is better in so many ways, much lower mileage and will give me another 10 years of reliable low cost motoring for £750.

Your Internet connection's bandwidth/speed may be more of a factor than the computer.

I tend to find that I run out of ideas about what I want to download before the hour runs out. Choose more things, 

It really is a great resource. 

Downloaded them all, had the usual rubbish with my computer where it just blinks and you dont know if anything has been downloaded, try again with a double click and same again, never know where stuff is going to be downloaded to if it comes at all, after some searching found them all including all the duplicates so they had downloaded very fast.

 

Far too many pages to ever consider printing them all, I need to buy a comb binding tool now!

On 30/09/2018 at 22:02, SuperbTWM said:

You haven't mentioned how old the car is and when you last changed the glow plugs, they don't last forever.

 

I owe you an apology my friend, you were 100ù right and I was 100% wrong, I had the harness removed yet I did not check their resistance so convinced was I that they would not all have failed and that they must all be working for it to start recently yet all 4 show the fault code.

 

I measured them today, 2 were open circuit, the others had around 8 and 10 ohms resistance to the battery -ve terminal or the head casting, dont trust my meter for low readings, it displays 0.5 ohms with the probes shorted, my regularly used one which needs attention showed 10 and 13 ohms but that displays 2 or 3 ohms with the probes shorted so I am guessing a higher resistance than the spec is that correct?

 

I need to get up to speed, I had never heard of ceramic glowplugs and though they were incandescent windings that would either be the correct resistance, open circuit or possibly shorted, do ceramic ones increase in resistance before failing?

 

Anyway thanks for pushing me to do what should have been obvious, it will be good to fix it before the really bad weather comes.

No need for an apology, just glad your issue can now be resolved easily.

 

IIRC the glow plug resistance should be very low, maybe 5 ohms and below would be a good glow plug but I could be wrong. If you buy a new set of glow plugs just test one out of the engine and see how quick it heats up and how much of it heats up and then compare it to one of the ones that read high resistance, you will probably see that it takes longer to warm up and usually just part of it may glow red.

 

I found the BKC engine to be very good in cold weather even with a few bad glow plugs, never got any smoke from mine whereas the AWX 130 in my Passat smoked like mad on cold starts until I put a set of plugs in it.

 

 

see the difference!

Make sure you give the engine a good heat/Italian tune-up immediately before trying to remove the glowplugs, you may fall foul of a broken plug if working on a cold engine.

 

It's not a guarantee to success but will improve your chances, and treat the plugs delicately, last thing you want is it to break in the engine at some future time.

 

~0.5Ω resistance when testing continuity between DMM leads is perfectly normal.

46 minutes ago, MicMac said:

~0.5Ω resistance when testing continuity between DMM leads is perfectly normal.

 

Unless you have fused leads, the RS ones are 2.5 Ohms 

Octavia 2 2006. I have error codes from VCDS log.

4 Faults Found:
17055 - Cylinder 1 Glow Plug Circuit (Q10)
            P0671 - 000 - Electrical Fault
             Freeze Frame:
                    RPM: 882 /min
                    Torque: 40.0 Nm
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Voltage: 14.36 V
                    Bin. Bits: 00101111
                    Temperature: 13.5°C
                    Bin. Bits: 10110000

I measured the resistance of each glowplug - 1490, 890, 15.3, 70 Ohms.  Seems I need to change them all, though I suppose the 3rd one might glow a little slowly  - I hope they don't break on removal!

On switching on the ignition the curly wire icon shows briefly on the dash and extinguishes.

Why is it so difficult to find where the fuse and relay are?  I looked in the under-bonnet fuse box - see picture. There is a relay there marked 100. I removed the relay and tested it on the bench - it works. With it removed the icon does not appear when the ignition is switched on. A good clue that this IS the glowplug relay.  Why is it so difficult to find out where the fuse and relay are?  I saw somewhere that someone thinks that the fuse may be under this fuse box and one has to remove the battery and battery shield to get at it by sliding it out sideways - I wonder if that is true?

I measured the voltage on No.1 glowplug connector, open circuit (All connectors disconnected) - no plugs; 6 Volts when the ignition is switched on and zero if I remove the relay! Where does 6v come from? I guess that it does mean I don't need to worry about the fuse though.