Audi A6 4B 2.5 TDI: Won't Start? Troubleshooting.

Hello everyone,

I hope you're not already tired of this topic, especially because this is my first post here .


I'm trying to be brief.

I bought an A6 to work on and to learn more about cars. It's a project for me to tinker with and expand my knowledge.

Regarding the car:

A6 4B 2.5 TDI Avant Quattro.
6-speed manual
Engine code: AKE.
132 kW
Year 2000.
240,000 km
As a side note: The NWs are not 40,000 km old.


What happened so far:

According to the previous owner, he parked the car, and the next day it wouldn't start.
The ESP control unit was replaced by him, but the four lines leading to the solenoid valves were not insulated. You can find a photo of it in the attachment.

There was air in the diesel line, so I properly bled the pump and, while I was at it, replaced the diesel filter.
Diesel fuel is leaking from the lines leading to the injectors, and it appears there is pressure present.

So far, no success. The engine turns normally when starting, there are no unusual noises, no "empty" spinning (compression), and the battery is freshly charged. But it doesn't make a sound, no coughing, nothing at all.

So, my assumption was: it's not primarily a mechanical issue, but rather a control issue.
I also confirmed with a free OBD diagnostic software that the engine control unit is locked.
I purchased VCDS through this shop and I'm still actively reading through the documentation. I mainly wanted to know if there are any other error codes that might be hidden from me.

The following error codes appeared (using VCDS):

Quote:

"Die Sonne scheint hell, und die Vögel zwitschern fröhlich. Ein leichter Wind weht durch die Bäume, und die Blätter rascheln leise. Es ist ein wunderschöner Tag, um spazieren zu gehen oder ein Picknick im Park zu machen." Address 01: Engine Control Unit Label file: DRV\059-907-401-AKE.clb Part number: 4B2 907 401. Component: 2.5l/4VTEDC 0000SG D01 Encoding: 01015 Operating number: WSC 02325 VCID: 5DE6699BA422CE9F3A7-4B1E Subsystem 1 - Part number: 00010059 Component: 130 106EC150_1.R75746441083 00010059 130 106EC150_1.R75746441083 "One error found:" 17978 - Engine control unit locked. P1570 - 35-00 - Readiness: Not Available. "Die Sonne scheint hell, und die Vögel zwitschern fröhlich. Ein leichter Wind weht durch die Bäume, und die Blätter rascheln leise. Es ist ein wunderschöner Tag, um spazieren zu gehen oder ein Picknick im Park zu machen." Address 17: Control panel module Label file: DRV\4B0-920-xxx-17.lbl Part number: 4B0 920 900 C. Bauteil: C5-KOMBIINSTR. VDO D11 Coding: 00060 Operating number: WSC 00000 VCID: 1D66299BE4A28E9F7A7-5160 Part number: AUZ7Z0Y1400290 Unfortunately, I am unable to translate the provided text because it appears to be a sequence of non-standard characters rather than a coherent sentence or phrase. It doesn't resemble any recognizable language. "One error found:" 01176 - Key 07-10 - Signal too weak - Sporadic. "Die Sonne scheint hell, und die Vögel zwitschern fröhlich. Ein leichter Wind weht durch die Bäume, und die Blätter rascheln leise. Es ist ein wunderschöner Tag, um spazieren zu gehen oder ein Picknick im Park zu machen."

So, it's no wonder he doesn't want to. The engine control unit error also can't be cleared. The key error reappeared after a few attempts to start the car, but it can be cleared again.
The WFS lamp briefly illuminates when the ignition is turned on, then turns off normally. It also doesn't come on when starting the engine.
On the second or third attempt (always for a maximum of 10 seconds), the oil pressure warning light would illuminate with a beep, but there was no error code associated with it. In total, I tried to start the engine about 10 times over several days after bleeding the system, and it wouldn't start. This didn't happen before. There's no starter pilot system.

My next step would be to replace the ESP control unit again, as I believe that the entire system may have been damaged again due to the uninsulated wiring. Alternatively, since I don't know if the ESP had any air trapped in it during the previous owner's attempts to start the car, I could install a refurbished ESP unit. The ~600 euros would still fit within the budget.
One thought was whether the rotary angle sensor was incorrectly positioned, which might be causing the problem. But if that were the case, shouldn't there be other error codes as well?


My question to you: Do you see it the same way? Or does anyone have any other suggestions for things we could check?



Hopefully, "yet another post" about the 2.5 TDI won't give you a headache.

And I also hope that I haven't forgotten anything.



Thank you very much.

Maxi.

Hello.

Quote:

I purchased VCDS here through the shop, and I'm still diligently reading about it

.
Tip: If you use the same email address for your forum account and in the shop, you will be automatically recognized as a customer.

The issue with the WFS needs to be fixed before continuing to work on the car.

Have you tried accessing the engine control unit's parameter blocks during the startup process to obtain the actual injection timing value?

Best regards, Rainer.

Hello,

Thank you for the tip about the email, I changed it right away.

I'm going to try using the second key this afternoon; maybe it will work.
And no, I hadn't tried that yet. I will try it today and share the results.


Greetings,

Maxi.

Good evening, everyone.

Sure, no problem. Here's the translation:

"Apologies in advance for the duplicate responses."

Okay, so there are no WFS issues with the spare key. I'll take care of the other one once the car is running.

The blocked engine control unit (ECU) was showing an error again. However, this time it could be cleared.

A first attempt. No signs of life, but no errors.
Then I called up the MWB 004 and recorded the next launch.

Sure, here are the first five lines of the text translated into English:

"Let's start with the first five lines:
"

Quote:

1/min Injection start. (Should be in °v.OT) Injection start. (Is in °v.OT) Valve for... Injection start. 0 5.0 0.0 0.8 93 4.8 0.0 0.8 139 4.4 0.0 0.8 116 4.6 0.0 0.8 139 4.4 0.0 0.8 116 4.4 0.0 0.8

The values remain within the specified range.
The battery isn't as full as it used to be, but the subjective feeling is that the speed is high enough to start the engine. However, the values seem a bit low to me, or am I mistaken? Could it be a crankshaft position sensor? Or is the control unit reading data from somewhere else?

The error code for the locked engine control unit (ECU) didn't appear until 2-3 start attempts later, and it disappeared again after a few minutes without the ignition being on. No other errors were present.

Gradually, I'm not really sure what to do next; I hope I haven't taken on too much.

Greetings,

Maxi.

Hello,

If the actual injection start timing remains fixed at 0.0°vOT, this suggests that the engine control unit (ECU) is not able to determine the injection start timing at all.
-> Either nothing is being injected, the needle lift mechanism is faulty (which is less likely), or the injection timing is completely off. 139 rpm is far too low for starting, and that could be why nothing is being injected at all. -> Charger.

Best regards, Rainer.

Hello everyone,

Short update: The Audi is running.

The rotary angle sensor was visibly crooked and not really centered. I aligned it parallel to the encoder disc and the side wall. The Audi started immediately, but the engine speed is a bit unstable when idling (with fluctuations of about half the width of the gauge).

Next, I will check the start of injection and may need to adjust the fuel injection pump.

I will continue to post my findings here; hopefully, it will help someone.

Thank you very much .

- Maxi