A6 C7.5 Multiple Errors and No Start Condition

[Bigdinner]

Hi,

I went to move A6 on Xmas day and the cluster lit up like Xmas tree and refused to start. The following errors come up on the cluster.

• Stabilisation control (ESC) fault!
• Tire pressure: system fault!
• Parking brake!
• Audi adaptive light: system fault!

MIL/CEL is on
Glow plug light is on
ESC, caution triangle light on
TPMS light is flashing

 

I plugged in my VCDS cable and it didn’t make for good reading. No comms with EMU!

I’ve tested every fuse for continuity (except the passenger fuse box and they were fine. Tested every relay I could in the engine compartment and luggage area, and all actuated and had continuity.

Today I disconnected the ECM and found water near the larger plug. The loom material is soaking wet and has signs of staining. There is a build up of dead leaves and crap bridging the gap from the passenger wiper drain to the ECM loom. Removing the plugs from the ECM, there are no corroded pins on the ECM itself, and both plugs look fine (no corrosion) when looking from the female side. I’ve yet to take the covers off the back of the plugs and inspect where the pins insert into the plugs.

I’m suspecting that the wet loom tape is the tell-tale sign of the problem, but can anyone offer any insight from my log above please?

Thanks in advance.

[Steve Q]

I think you've hit the nail on the head to be honest. See if you can dry out the emu and get all drain holes clear of leaves etc. Once dry see if ye problem persists. If it does then replacement is usually the only option 

[Anton8]

Hi Gareth

Have you checked the battery. Could be a cell has gone down.

Tony

[Bigdinner]

@Steve Q thanks for responding. I’ve had this all apart today in the breaks in the weather, and there are no signs of corrosion anywhere, but the wiring harness fabric is still soaked. I’ve cleaned the crap up, but I’m not sure this is the problem now.

After checking all fuses in the SA fuse holder (in the plenum chamber), fuse SA9 is showing 0 volts. According to Elsawin, SA9 is for Voltage Stabiliser -J532-, and ALSO Engine Control Unit -J623-!!!

I m having trouble understanding where this feed comes from in the first place though so that I can work backwards.

 

@Anton8 thanks for replying. I got a battery tester today, but haven’t had chance to use it yet. The battery keeps going low with all the ignition on testing. Yesterday I had it on charged up to 12.7v when I put the multimeter across the Jump start point in the engine bay. It’s not dropped to 11.5v as possibly the DRL’s are annihilating it with the ignition on during my checks.

hopefully the weather holds off and I can charge and test tomorrow to rule it out. 

[Magnet]

Hello Gareth,

Sorry to hear of your issues, but pleased you have been able to find ‘culprits’. 
Re. eliminating the battery via. testing:- what battery tester do you have? 
If it were mine, I would be getting it tested ( after charging with an ‘intelligent’ charger - as you’ve been using??) at one of Halfords shops. They will be able to check the all important CCA  as well as other parameters. 
Kind regards,

Gareth. 

[Bigdinner]

Hi Magnet,

Unfortunately the problems still persist unchanged. I have found 0 volts at the ECU fuse in the engine bay which has taken me in another direction.

I bought a battery tester from Amazon today, but ran out of light so can’t test the battery today. For reference, the charger I bought was a Topdon Car Battery Tester BT20

Topdon Car Battery Test BT20

I only have a dumb charger to charger the battery with so will charge it again tomorrow and use the tester to rule it out, hopefully.

[Magnet]

Thanks Gareth,

Can I take it your battery is an AGM type? If so, it should be charged with an ‘intelligent’ cycling charger to avoid battery damage. 
Kind regards,

Gareth. 

[Bigdinner]

I’m not sure if it is an AGM battery TBH. I have been charging via the Jump Start terminals in the engine bay. Would the battery not be protected via some kind of BMS in that instance?

Thanks,

Gareth

Edited December 29, 2023 by Bigdinner

[Magnet]

Hello Gareth,

If it has stop/start, then it’s likely to be AGM. 
I would not have thought the BCM would protect it from continuous charging via. old style chargers - but I could be wrong.

Kind regards,

Gareth. 

[Steve Q]

My gut is that it's not the battery but I'm only guessing 

[Bigdinner]

2 hours ago, Magnet said:

Hello Gareth,

If it has stop/start, then it’s likely to be AGM. 
I would not have thought the BCM would protect it from continuous charging via. old style chargers - but I could be wrong.

Kind regards,

Gareth. 

Yes it has Stop/Start so probably AGM. I will charge again tomorrow (slowly) and keep checking voltage periodically with a multimeter. It did charge to 12.7v yesterday, but I drained again with all my testing. Once charged, I put the new tester on it to see its health.

2 hours ago, Steve Q said:

My gut is that it's not the battery but I'm only guessing 

I’m not convinced it’s the battery either Steve. As far as I know, it’s the original battery so it’s done well (8 years old), but I not convinced that a tired battery would result in 0v measured at the ECM when other systems seem to be quite happy.

Will check tomorrow and report back.

[Steve Q]

21 minutes ago, Bigdinner said:

Yes it has Stop/Start so probably AGM. I will charge again tomorrow (slowly) and keep checking voltage periodically with a multimeter. It did charge to 12.7v yesterday, but I drained again with all my testing. Once charged, I put the new tester on it to see its health.

I’m not convinced it’s the battery either Steve. As far as I know, it’s the original battery so it’s done well (8 years old), but I not convinced that a tired battery would result in 0v measured at the ECM when other systems seem to be quite happy.

Will check tomorrow and report back.

Please keep us posted on how you get on 

[Magnet]

Thanks Gareth,

It seems as if there could be more to this than the battery, but if this is the original, then it had done its fully serviceable time a couple of years ago. It would be an investment to replace it, even though you might find it’s not the major culprit, and the aggravator may have been the water ingress. 
Kind regards,

Gareth. 

[Bigdinner]

Thanks Gareth.

Just charged and checked the battery (it’s an EFB type battery, not AGM). Passed all tests with flying colours with 100% charged and SOH >90% according to the tester. I think this rules out the battery being an issue although I will consider replacing once I’ve sorted the main problem.

Gareth.

[Bigdinner]

Cracked it! 

Stupidly I was overlooking the fact that multiple modules were reporting 0 volts at terminal 15 when the ingnition was switched ON (which is pretty obvious if I looked at the VCDS logs properly).

Terminal 15 relay 2 (under the steering column dash panel) must’ve got stuck which was preventing it from closing and giving ingnition power.

I removed and tested the relay on the bench and it worked 100 times out of 100. I will order a new one so that I have a spare on hand.

Moral of the story, read the damn VCDS logs fully!!!

Hopefully this helps someone else out in future!

Edited December 31, 2023 by Bigdinner

[Steve Q]

Glad you got sorted 🙂

[Skubiss]

645 relay under the steering wheel - it is not next to the 644 but a little deeper.