Intermittent fault: Engine control unit and pump-nozzle valve issue

Hello diesel mechanics,

"I've been having a problem with my A6 4B with a 1.9 TDI AVF engine for almost two years."
6-speed manual transmission, and I'm stuck. (VCDS log below).

The vehicle will be driven five days a week, with two trips of 30 km each day, and on weekends.
Sometimes it's like this, sometimes like that.

Occasionally, and in a way that is not reproducible, the engine check light comes on, and the engine...
shudders. Sometimes the engine stalls, but it can be restarted immediately.
Sometimes it doesn't turn on, but it usually needs to be restarted.

The procedure of restarting sometimes works on the first try, but sometimes it doesn't.
Only after 5 to 10 attempts, or after waiting for a few minutes.

So far, I have replaced the jumper wires to the PD elements and the tandem...
The pump has been replaced with a new part. The diesel and air filters are also new.

The actuator diagnostics and the inspection of the VTG (Variable Transmission Gear) revealed no errors.

However, the turbocharger forces a certain amount of oil into the airflow.

A long time ago, I installed a Steinbauer P-box, according to the manufacturer's specifications.
It increases the value of the item by 20%.

Hopefully, I haven't forgotten any essential information about the vehicle.

Has anyone else experienced similar problems and been able to resolve them?

I am grateful for any help.


Best regards, Bert.

Hello,

Relay 109 is a strong candidate. The relay may also have a different name; it's best to obtain a wiring diagram for your vehicle. It provides power to the engine control unit (ECU). You can find countless posts on this topic in this forum.
Also, also make sure that the plugs and cables on your device are in good condition.

If you have an old fuse box on the battery, check and replace it as well. It can cause such disturbances in the vehicle's electrical system that the ECU resets.

Best regards, Rainer.

Hello Rainer,

The relay is already a good clue.
I will exchange and report.

Best regards, Bert.

Hello,

I now have a new relay 109, but I have no idea where it is.
that is built-in. Is that thing in the box inside the water tank?

It should be located in the water tank. From the driver's perspective.
It can be tricky to get the lid open .

Sure, here's the translation:

"Note:"
It's possible that on the Passat, it's not labeled "109," but rather has a different designation. If you bought a "109" model without any specific information, it's possible that it might not fit .

I know from the Passat 3BG that there's a double contact relay there, and it's labeled with the number 219.
Similarly, I had to replace the starter on my Audi A4 B5 with the AJM engine; it would also occasionally fail to start, but instead of not starting at all, it would take a delayed start (around 6-7 seconds). Since then, no problems whatsoever.

...so, I replaced the relay 219. Item number 109 is not available in the online store.

Error codes read and cleared.

The old relay actually looks to be in good condition on the inside. Let's just wait and see...

Most of the time, it's not the relay itself that is worn out, but rather that the solder joints have hairline cracks.