Standby Power Failure: Troubleshooting Potentiometer.

Hello.
Unfortunately, I couldn't find anything suitable using the search.
Vehicle: 1999 TDI 90 hp/AHU engine, 210,000 km.
Following error:
I was driving on the highway at 140 km/h when, without any warning, the accelerator stopped working. I let the car roll to a stop on the shoulder. The preheating indicator started flashing, the car wouldn't accelerate, and it remained at idle (limp mode). All other functions were working. I turned off the engine and restarted it, and the car started working normally again.

After more than a month, the exact same thing happened again - practically in the same location. This time, a restart doesn't help. I drive slowly (thankfully, a maximum of 60 km/h) to my workshop. There, the error message "Potentiometer" is displayed. So, the very expensive part (about 350 Euros) is replaced. I pick up the car, and on the very same day, it happens again, but in a completely different place...

This time, the VW technician said that the brake light switch could also be the cause, so it was replaced. Now, there are 14 days or 600 km of trouble-free driving, until it happens again, almost exactly in the same location where it has happened twice before.

One might think that there are some kind of electronic jammers at this location that are interfering with my car. However, I still believe it's just a coincidence, because it happened once 100 km away. And in the place where it has happened 3 times, I drive past 4 times every day.

Okay, back to the workshop: now it's supposed to be a switch on the clutch. That switch has also been replaced. I've now driven another 100 km without any problems, but I'm still not entirely confident about it.

Has anyone ever encountered something like this before, and does anyone have any idea what it might actually be?
Thank you in advance for your help!!!!!!!

Hi,

Please use the search function to read the error codes from the engine control unit's memory after the error has occurred; otherwise, it won't help.

Best regards, Rainer.

Sorry.
"However, the error memory showed three times that the potentiometer on the accelerator pedal is defective! But that part was already replaced the first time..."

ascienna wrote:

Sorry, but the error memory showed 3 times that the potentiometer at the accelerator pedal is defective! But that had already been replaced the first time...

Sure, here's the translation:

"Here's a small tip:"

Faults in the wiring harness between the MSG (Modular Sensor Group) and the pedal can produce electrically similar symptoms to the potentiometer itself, and therefore also the same error codes.

And no, I don't know where you should start looking.

These are 6 wires connecting the accelerator pedal to the engine control unit.

If in doubt, completely rebuild all 6 units from the bottom up, in one go.

In Audi vehicles (since you haven't specified the model), there are three connection points on the original wiring harness: one at the accelerator pedal itself, one in the engine compartment at the rear, and one in the ECU (Engine Control Unit) located in the water reservoir area.

At each of these connection points, for example, a pin could be slightly widened... that's enough to cause an instability, and then you'll have exactly that kind of error.

I had the same problem with a new A3... I just routed all the cables directly from bottom to top, and it worked perfectly.

Hello Vagtuning,
That's a good starting point. If the error occurs again, please let me know! Thank you!
My car is a Passat Variant.
What does a wiring harness like that cost?
Best regards, Walter.

You can't just buy it ready-made; you'll have to build it yourself.

'Please provide 3 replacement cables with pins on the bottom (with 6 pins on each side, totaling 6), then 6 pieces of unknown 2-meter cable, a total of 12 crimp/solder connectors, and 3 more replacement cables (with 6 pins) for connecting to the MSG.'

Or 6 wires of the correct length, and individual pins from the top and bottom, sourced from an electronics store if available, and then crimped yourself.

However, in my opinion, this is usually the weakest point of the whole thing, so I would personally opt for option 1.

It's usually easier and results in a better connection when you properly join two cables together.

Unless you use a suitable pliers to properly grip the crimps.

Otherwise, you'll just create another source of error for yourself.

Soldering and using heat shrink tubing should also work, if done properly.