A6 3.0 TDi Quattro - Multiple Electrical Problems including cutting out

[seventh-heaven]

My brother in laws car has developed a significant number of problems that ultimately made it cut out and not restart on a couple of occasions.

Symptoms as follows:

• Engine cut out and would not restart - happened when changing the temperature on the A/C. Restarted after a while but noticable that ECON light on on A/C and compressor would not run. ECON light since extinguished and A/C working normally;
• Once at home run the engine and would cut out for no apparent reason after a short period - would restart sometimes straight away, sometimes after a while;
• Main engine cooling fans running when the key is not in the ignition. Put the key in and turn to first position and fans stop;
• Fuel Pump in tank runs all time including when no key in the ignition;
• Downloaded fault codes using VAG-COM - list must have nearly filled the hard drive on my computer it was so long;
• All fault codes saved on log and then all cleared. After this the cutting out symptoms have disappeared but Fuel pump symptoms remain all the time and cooling fans occasionaaly run. Suddenly start up randomly even if car has not been used for hours and is locked and no key present;

Fault Codes:

Post initial clearing many appear to be due to low voltage - no suprise as battery went very flat from fans and pump running. However following look interesting:

Engine Controller 18018 - Internal Control Module Check Sum error

Gearbox Controller 18258 - Power Train Data Bus: Missing Message from ECU

ABS Controller 01314 - Engine Control Module 004 No Signal/Communication - Intermittent

A/C Controller 01314 - Engine Control Module 008 - Implausible Signal Intermitent

Central Electronics 00003 - Control Module 014 Defective (although this dates from more than 2 years ago!)

Following attempted clearing of all codes only 2 remain being:

Central Electronics 00003 - Control Module 014 Defective (although this dates from more than 2 years ago!)

Engine Module 18061 Please check DTC Memory of ABS Controller P1653 - 002 - Lower Limit Exceeded


A couple of additional issues that may or may not be related:

• Have previously had to repair damage due to water ingress. This was in drivers side electronics box under the bonnet (the one under wiper mechanism). This was as a result of a previous owner/garage having broken the lid and not replaced it - seal was damaged. Glow plug module submersed and runied, had to be replaced and all connections cleaned of much contamination;
• Shortly before the faults developed the car spent time at a bodyshop having repairs that would have included welding.

Next steps:

1. Check the previously mentioned electronics box for any repeat of the water ingress;
2. Check similar box on passenger side which I beleive contains the engine ECU for any water ingress;
3. Find fuel pump controller/relay and swap with my own car (identical apart from Manual v Auto) to see if fault transfers and possibly similarly with Fan Controller;
4. Examine if Engine ECU is same between cars and do the same.

Any other thoughts or suggestions appreciated!!

[joshA6]

it's seems like an ECU problem.

Personally, I would check, double check and triple check all your fuses first. Had a similar problem with a Mk5 Golf diesel with multiple random faults. Turned out to be a blown fuse in the engine bay

[coolraj003]

A lot of Audis suffer from water damage to electrics due to clogged drain holes. When you mention the driver side elctric box was water damaged, did anyone check the passenger side box as well as they are more prone to water damage?

You can check out a few threads on the forum about water in passenger side footwell, some eventually damaging the CD rack and nav drive as well as ECU box.

Raj

[seventh-heaven]

Water damage was due to damaged lid on box and there was ne reason to beleive that the other box was damaged at the time.

Is this version of A6 subject to this problem as well? I am aware of the problems with older versions and all the other threads I can find refer to the blocked drain holes under the battery. On my C6 the battery is in the boot!

Thanks

[seventh-heaven]

Well coolraj003 was proved to be right! On opening up the passenger side box found a very high tide mark and some water in the box at the time. 2 relays in the base of the box that had been submerged and were corroded. One is fuel pump relay and that was completely useless - hence fuel pump running constantly, and the other is the main power relay for the engine +12V feed which inlcudes feed to ECU.

Having taken them out and looked at them car would not start at all - so new ones ordered and installed. Still no good. Further investigation revealed that the +ve and -ve signal cables to the 12v feed relay had both corroded so much that disturbing the relay base to remove and install the relay had made them break away. Re-crimped, cleaned all terminals, added contact grease and hey presto a functioning car with no fault codes.

Couple of thoughts on reflection:

- My sister had got to the stage of wanting to sell car convinced it was a lemon that was going to continue to have problems - how many more people do that for the sake of a £20 relay and 2 crimps - and how much would a specialist have charged to find the problem! Makes you grateful of having the skills to do it yourself!!
- How have Audi managed to design a second major version of the A6 that has the same inherent problem as the last one - poor design and or feedback from service teams to design teams!

[coolraj003]

Sorry to hear that it was the problem but at least you have got em sorted out without having to fork out major £££. To be honest I was not entirely sure that the issue still remains on this model of A6. I know for a fact that one of my colleagues has a 55 A4 Avant and she suffered from this issue. I dont know whether the newer models have been sorted out or not. I check for any debris and gunk in the area at the bottom of the windscreen to check for any water due to clogging. Just yesterday I cleaned out a lot of dead leaves from this area. I might just be paranoid but i think its better to be safe than sorry. I can bear with the thought of minor bruising to the fingers than to shell out on electrical damage to the components.

As long as the issue of people wanting to sell their cars due to this issue, I think you have been lucky that it was just a case of minor damage to connectors etc. In some cases water damages the CD Rack, Nav Unit in the glove box and also the ECU. Then you are talking a lot of money which is bound to lead people to think that its not worth it. And as far as feedback from service teams to design teams is concerned then I think you would be able to count all the cases on one hand where the Audi technician have actually taken responsibility for any major issue like that on the design fault whether it be the water damage issue, oil pump issue etc. If they can get away with charging the customers in 95% of times in cases due to design failure then why bother rectifying them or feeding it back to design team as it would be loosing a lot of potential income.

Hope this wont be happening again but I would just check it now and then just in case.

Raj

[Andyase]

Have the exact same issue in my a6 3.0tdi quattro. I emptied some water from the box today, ive had a flat battery and the in tank fuel pump not working. I am waiting for a removal tool for the wipers and will then replace the relays and check the wiring. Did you find out how the water got in the box?

Andy

[gupsterg]

Underlined is concise info...

from 1st post in thread...

A couple of additional issues that may or may not be related:

• Have previously had to repair damage due to water ingress. This was in drivers side electronics box under the bonnet (the one under wiper mechanism). This was as a result of a previous owner/garage having broken the lid and not replaced it - seal was damaged.

then 3rd post

water damage to electrics due to clogged drain holes. When you mention the driver side elctric box was water damaged, did anyone check the passenger side box as well as they are more prone to water damage?

then 5th post

Well coolraj003 was proved to be right! On opening up the passenger side box found a very high tide mark and some water in the box at the time. 2 relays in the base of the box that had been submerged and were corroded. One is fuel pump relay

[sparker]

Andyase,

Might be to late but you can easily remove the relays in the ecu box without needing to remove the wipers. I have just taken mine out to check them (both clean thankfully).

Remove the two screws from the centre of the lower window plastic trim so it can lift slightly. Remove the five or six? screws from the ecu box. All but one is obvious. There is one screw out of sight on drivers side but is easy to reach. There are no screws at the far rear, the lid clips in.

Once open and lid removed you have room to remove the clip which holds the ecu in place. The clip can be pushed down on the driver side then push out with a medium screw driver to un clip (hopefully you will see what I mean when you try, it's easy to work out)

When the ecu is free to lift up then you have ample room to get to relays. If you need to replace wiring spades then you would need to see if you can get the wiring out I didn't need to but the loom does lift out of the box.

Hope it all goes well.

[MarkTM]

Does anyone list part numbers for any of the above, I rang Audi to order a new relay and fuel pump ECU but they couldn't find them??