Engine Control Unit No Communication Audi A8 2.5 TDI

Hello,

I'm currently in the process of repairing a colleague's car.
A8, 2.5 TDI, with AFB engine. Year of manufacture: 1998. Mileage: 200,000 km.

He parked the vehicle at home yesterday evening. This afternoon, he tried to drive it again, but the car won't start. The engine turns over normally, but doesn't fire up. In the instrument cluster, the preheating indicator, ASR (traction control), ABS (anti-lock braking system), and the engine electronics warning light are constantly illuminated.

I then made a diagnosis, but I can't access the engine control unit. I can communicate with all other control units, but there it always displays: "No communication with the engine control unit!" This error appears regardless of whether I'm connected to the climate control or brake control unit; everywhere, the same error message. The power supply relay in the water tank is engaged and you can hear it switching. So, there is power getting there. All fuses are okay.
What do you think?
Is the engine control unit (ECU) broken, or what should I do? Thanks.

luiggi wrote:

Ist das Motorsteuergerät kaputt,oder wie solllte ich vorgehen? Thank you

.
It initially sounds like either a) the MSTG is not receiving power or b) has lost its connection to the...
Data bus (the '98 A8 may also still have a K-line).
I would start by looking into the wiring.

Best regards, Micha.

I'm not getting any communication with the pump control unit. If that's the case, the pump is likely faulty. Could there be a wiring problem in the K-line?

Hello,

This morning, I checked the relay for the power supply to the engine control unit again. It was functioning correctly.
After that, my acquaintance transported the vehicle to Audi for repairs, as I'm not very knowledgeable about electrical systems. Then, in the evening, he called me and said that the engine control unit was defective! The cost is approximately €1100 plus installation and adjustments.

I personally suspect that the problem might be with the cables.
What's strange and surprising is that he parked the vehicle at home, but the next day, he wanted to drive it again. Could the control unit still be dead in that case?
As I said: I can access all the other control units, but for each one, it says something about the "engine control unit"...?
The climate control unit displayed the message: "CAN bus - no data connection to the engine control unit."

What do you think about that? Best regards.

So far, I haven't experienced a situation where a storage device failed so easily and unexpectedly while in a seemingly peaceful state (like during sleep).
passes away.
Then it's more likely to be a weasel that has damaged a nerve or caused an abrasion.
(This used to happen with early G3 gasoline engines; there was a spot that wasn't properly deburred, and...)
K-Line got caught ).

Before I spend over €1100 on something that might not work, I'd rather try building my own adapter and see if it does the job.
The section on the table addresses the issue of diagnosis.

Best regards, Micha.

Hi,

I also doubt that simply replacing the control unit will solve the problem. But is it really that easy to access and interact with the control unit when it's removed? Or what exactly needs to be done for that?

Here's the translation:

"One more question: Over how many cables does the diagnosis actually take place? Can someone briefly explain how this is done? Thanks."

To operate a Stirling engine on a table, it should have three or four connections for the generation process.
To be connected: 12V power, ground, K-line, and possibly an additional 12V ignition power supply.
The 12V power supply, ground connection, and K-line also connect to the diagnostic interface – that's all there is to it.

Best regards, Micha.

Hello,

Just wanted to let you know quickly that the vehicle is working again.
Cause: As suspected by the workshop previously, the engine control unit is defective! Price: €1500 including installation. Regards, Luigi.