Issues with glow plugs - or something else?

[Richster]

Hi - I have had an issue with my engine management warning light for the past few years, though if I reset it (using VCDS lite PC software) just before the MOT it will stay off long enough to pass! The engine seems to run perfectly in general.

When looking at fault codes, the diagnostics (again VCDS lite) shows glow plug faults on random cylinders. I plucked up the courage to change the plugs which was surprisingly easy (it was still on the orginals, mileage is IRO 130K) and thought I'd fixed it, but the light is back on.  After a reset, I can normally drive for about 30 mins or so before the engine management light illuminates. Normally this happens an engine restart or two after I reset it (maybe after there are a certain number of faults logged?) 

I also tried changing the glow plug relay previously, but that had no effect.

I'm beginning to think the issue might be something entirely different? The other fault which pops up in the engine diagnostics from time to time reads something like databus drivetrain missing message from instrument cluster.

The other intermittent fault I have is with the ABS, which seems to be somewhat weather dependant. Sometimes the ABS and traction warning lights illuminate, other times just the traction control. An engine restart generally clears these, but they can pop up a few minutes later. 

Does anyone have any thoughts? Or perhaps someone local has some better diagnostic equipment and would be willing to assist for a beer or two? I'm in Watford/Bushey area Both of these are MOT failures but I can usually get them to be off for the duration of the test.

Thanks



 

[Guest]

1996, surely this is a Mk.I?

[J.R.]

On the MK2 glowplug failure registers a fault code but does not bring up a MIL light, or at least it didn't on mine, they are not mission critical.

 

I doubt the MK1 even monitors the circuit.

[SuperbTWM]

What is the actual year/model?

[Richster]

Apologies - have updated year in my profile. It's a 56 plate - MkII, 1.9TDI

I'll run the diganostics again (since I changed the plugs and the engine management light came on). Is it possible VCDS lite is giving me misinformation? I'm expecting to see the same fault codes. Will post here.... 

Re faults about specific plugs/cylinders, there's a rubber harness which connects them all together - it looks like the connection is common to all 4.

Edited 2 November, 2023 by Richster

[misterpie]

We had a 06 plate VW Passatt (same platform?) 1.9TDI PD engine that would throw MIL light on glow plugs occasionally. Never did fix it. We had new glowplugs fitted too which seemed to help for a while.
I had limted success changing a relay under the fuse board, under the bonnet - 2006 VW Passat B6 Estate 1.9 Tdi Bosch Glow Plug Relay 0281003038 - Certaily helped on our car - but changed it a few times over the years when the fault came back.

Felt was a loom problem and the relay was a placebo - But, I could clear the fault every time (weekly) and after changing the relay it was fine for months.

Ran fine, bit smokey. We got shot at 155K in 2018. She's still going strong looking at the MOT history - 221K in July 23 🙂

[Richster]

Thanks for the info on the Passat

So I stand corrected - I am no longer seeing plug errors. From a check just now:

005712 -  Powertrain Data Bus: Missing Message from Instrument Cluster
           P1650 - 000 -   -

Have seen this before, I thin this might be somewhat of a red herring from what I've read elsewhere
 

005697 - Shareware Version. To Decode all DTCs
           P1641 - 000 - Please Register/Activate

Internet tells me this relates to air con? I know the system isn't working (has a gas leak) but surprised this causes a 'fault'

 

001025 - Shareware Version. To Decode all DTCs
           P0401 - 000 - Please Register/Activate
Internet tells me this is an EGR valve issue - seen this a while back. I think there is a function in VCDS for testing the  valve, I don't know if that works in the free version I have. That's probably a good next thing to try. May just need a clean up?

 

005379 -  Load Signal from Alternator Term. DF: Implausible Signal
           P1503 - 000 -   -
Not seen this before..... suggests alternator fault or fault with ECU -> alternator wiring having read other posts on here. Surprised to find this showing

 

[T2000]

How old is the battery?

[Richster]

Not particularly -= but I rarely use the car as I WFH. After not using the car for a long time, I drove it about 20 miles. The light waning light came on during the return journey after about 5 mins. 

I've also been keeping the charge topped up from time to time when not in use.

Edited 2 November, 2023 by Richster

[T2000]

56 minutes ago, Richster said:

Not particularly -= but I rarely use the car as I WFH. After not using the car for a long time, I drove it about 20 miles. The light waning light came on during the return journey after about 5 mins. 

I've also been keeping the charge topped up from time to time when not in use.

Only reason I say is that I had similar issues as yourself throwing all sorts of comm errors and dash lights, as you I didn't use mine a huge amount due to WFH, I bought a new battery and fitted it which cured the slow starting but it still threw errors, I took the new battery off and put it on an intelligent charger for 24 hours, when I connected it the battery was 11.9 volts (should be around 12.5), must have been sitting on a shelf a while, anyway it hit full charge put it back on and clear all faults and it was fine then.

[Richster]

I haven't run the engine since the last drive when the error popped up. I just measured the battery voltage with a digital multimeter - 12.1V

I think it's not more than a year or so old. I do get through them due to not using it much! It's a Bosch.

Edited 2 November, 2023 by Richster

[T2000]

On 02/11/2023 at 21:04, Richster said:

I haven't run the engine since the last drive when the error popped up. I just measured the battery voltage with a digital multimeter - 12.1V

I think it's not more than a year or so old. I do get through them due to not using it much! It's a Bosch.

Yeah my new one was Bosch, I suggest taking it off and put it on a condition charger, 12.1 is low

[J.R.]

A not abnormal reading if someone does not appreciate the load that is still being put on the battery when they think they have switched everything off to measure the voltage.

[Richster]

In an attempt to solve the EGR fault, today I took out  the  valve and gave it a good clean out (the port at the bottom where the exhaust gases enter was full of gak - non technical term). The valve definitely moves freely now (I could push it up with a screwdriver) though can't confirm if the vacuum system is working correctly. When I test drove it I noticed a kind of squealing sound from leaking air when accelerating hard which may have been some trapped dirt? After a few hard accelerations the issue went away. If anyone's looking to do this - it's not particularly tricky to get the valve out, but there's very limited space to work with hex keys (2 sizes needed). Moving the duct out of the way behind the engine helps a little. I could get a replacement valve for not much, but I'm not sure that's the root cause of the issue.

I still see the P0401 insufficient flow message in the diagnostics, though the engine management light didn't illuminate. I'm confident after a reset it will stay off long enough to get through the MOT.

 

Meanwhile the traction control tends to illuminate randomly during a drive. VCDS lite doesn't give me any specifics on that (I'm not sure I can read all the modules, I notice the 'auto scan' feature only mentions the Octavia MK1, not the MK2). Restarting the ignition clears the error. The rear offside sensor was replaced maybe 8 years ago, I'm thinking it could be related to that? How would I get this diagnosed? Ask a garage?

 
 

 

[Breezy_Pete]

Try scanning just the ABS module.

[Richster]

I can't scan it with the version of VCDS I have (doesn't recognise it). I'm not sure if it's because I have the free version or it's an Octy Mk 2 which I don't think is supported. May be worth asking a garage nicely. ABS works fine mostly (tested it with a few emergency stops), I think the issue is likely an intermittent reading from one of the sensors. My suspicion would be the one which was replaced before.

[Richster]

I can't scan it with the version of VCDS I have (doesn't recognise it). I'm not sure if it's because I have the free version or it's an Octy Mk 2 which I don't think is supported. May be worth asking a garage nicely. ABS works fine mostly (tested it with a few emergency stops), I think the issue is likely an intermittent reading from one of the sensors. My suspicion would be the one which was replaced before.

Some more research suggests the lite version of VCDS can only read the engine module. Probably I'm best off asking a garage nicely rather than splashing the cash on the full version.

[Richster]

Update....

I got the car through it's MOT with no waning light issues. The EGR issue may / may not come back after yesterday's valve clean up, will keep an eye on that.

I slipped the garage an extra £10 and they kindly hooked it up to their own diagnostic equipment. Fault reported on front driver side ABS sensor so will swap that out. I would think the wiring harness is also worth a check here.

Today is a good day!