VW T4 2.5 TDI ACV Error: Throttle Position Sensor

Hello fellow diesel mechanics!

Unfortunately, my 1997 T4 with the 2.5 TDI ACV engine is having problems.
Currently, the car has 560,000 kilometers on the odometer.
For the first time, the symptoms appeared a year ago, but they went away again.
It happens more frequently and lasts for a considerable amount of time.
The Bosch throttle position sensor (part number 0 205 001 020) was replaced with a used one, but the problem persists.
The car is going into a limp mode, meaning the engine is revving to 1100 RPM and not responding to the accelerator pedal. The fault memory shows code 00777 for the throttle position sensor (G79), indicating an intermittent, implausible signal.
Before the error occurs, it automatically increases the throttle slightly.
This would suggest an increasing resistance, for example, in the wiring harness.
I have to mention that the car was involved in a serious accident 10 years ago, during which all the cables connecting the winch to the control unit were severed. I believe I soldered these connections very carefully and insulated them with heat-shrink tubing.
However, I have a feeling that this very connection might be causing the problems.

My approach would be to disconnect the cables that run directly from the accelerator pedal to the control unit, in this case the MSA15 with its aluminum housing, from the accelerator pedal sensor connector and connect them directly to the engine control unit.

Do you have any other ideas about what it could be?
During my online research, I found very few problems reported with this potentiometer, and unfortunately, those who had solutions were hesitant to share them.
Relay 109, which supplies power to the potentiometer, was replaced after the accident because it was burned out.
However, if the problem originates from relay 109, I believe we would also see issues with other control units.

However, I'm not 100% sure about the pinout of the MSA15, and I don't want to just start tinkering with it without being certain.

The 15-pin configuration of the MSA that I found doesn't seem to completely match the wiring diagram.
Can I post wiring diagrams here?

Thank you very much for your thoughts and ideas on this matter!

Have you ever looked in the MwB (presumably a technical manual or database) to see what happens when the pedal is activated?

Hi, Hello,
You can find the correct wiring diagram at Erzwin (I just checked). Wiring diagrams for Volkswagen Transporter models 1996-2003, type 7D, etc.
hg
Herbert.

Good evening.

From your potentiometer, three cables lead to the T10 connector on the relay board.

brown leads to Pin 7 (connector T10) and from there, as brown/yellow, to Pin 55 on the engine control unit.

The pink wire goes to Pin 6 (connector T10) and from there, as brown/yellow, to Pin 57 on the engine control unit.

The white wire leads to Pin 1 (connector T10) and from there, as either white or black, continues to Pin 15 on the engine control unit.

Take a close look at the connector - these tend to corrode and cause the error described.

Best regards,

Michael.

Rüdi wrote:

Have you ever looked in the MwB to see what happens when the pedal is activated?

Unfortunately, my girlfriend was driving at the time, and she wasn't familiar with how to use VCDS.
After that, it will always display the correct percentage, from 0% to 100%. Given that it's easily accelerated, I assume the resistance increases at that moment.

I have access to Erwin, but I haven't found the pin assignment diagram for the MSA15 yet.
The G79 schematic shows it as Ich_Can-nix described, but that doesn't match the colorful pinout diagram.
Unfortunately, I can't go watch [the game/event] because the best team is located 500 km away by bus.
I still have Pin T8 from the F60 at 68/65, and Pin T5 at 68/62.
Or is this the wiring diagram for the newer G79, which came out starting in 1998 and is already integrated into the accelerator pedal?

Edit: F60 is actually the throttle valve, which he doesn't have, and T8 is the kickdown switch, which he also doesn't have because it's a manual transmission.
Okay, I will bridge those three cables.

Hi,
I would be cautious about using the term "überbrücken" (bridging/bypassing), as it might be the case that, for example, the "Kick-Down switch" in a manual transmission always needs to be active.
Regarding Erwin, there's a document called "Wiring Diagrams" available in three versions (based on production years), each containing a section specifically for the ACV engine. Additionally, there's the "Engine Control Unit (ECU) Reference Manual" for the engine, which includes sub-sections for the TDI engine titled "Check Components and Functions." I can only see the table of contents without paying, but I'm familiar with the content of the Audi 80 B4 as indicated in my signature.
hg
Herbert.

Thank you for your suggestions.

I'm just a little unsure about the pinout of the MSA15.
According to the colorful list, the pins would be 23, 24, and 11.
I have another diagram that shows this, see below.
And most often, people are talking about 80 pins, not 68.
I'd really prefer not to connect anything incorrectly there.