VW Passat: Strange MWB 1/2 & 8 Readings

Translated on 22-10-2026, 1:05.

Here's a Passat with a performance issue. I checked the measurement block 10, and the boost pressure sensor (F96) was only showing 700 mbar. I opened the turbocharger, but the bleed valve wasn't working. I also found some oil on the hose leading to the boost pressure sensor in the engine control unit. After reassembling everything, the altitude sensor reading is correct again, but the car still lacks power.

In the MWB 1/2, it shows me a reading of 25mg per injection at full throttle, and a voltage of 2.5 volts, which is obviously too low.
However, in product MWB 8, the small dose is 40mg per injection.
Is the value in MWB 1 a feedback signal from the quantity setting device? So far, I've only seen logs with MWB 8/3 and 8/4, which correspond to MWB 1/2.

Translated on 22-10-2026, 1:07.

Hello,

The MWB 8 looks fine.

If the fuel injection quantity is too low in module MWB 1, even though module MWB 8 is correct, the car is likely running in emergency mode.

Error memory? Is the dataset original or corrupted?

Best regards, Rainer.

Translated on 22-10-2026, 1:08.

"The error memory indicated a faulty control unit, but the error could be cleared after opening the control unit. The two PLCC32 chips are the originals, or at least, there are no sockets installed."

I also had a fault code related to the fuel shut-off valve, a mechanical error. Unfortunately, I didn't save the code, so I don't remember the error number.

Currently, there are no errors.

Translated on 22-10-2026, 1:09.

Quote:

Is the value in MWB 1 a feedback from the quantity setting device

Yes, that is the amount of fuel the pump is supposed to deliver.

Maybe the engine control unit (ECU) is actually defective?

"Start-Stop values from the interlocking system test? I don't recall the exact measurement block right now, but it has been posted several times in this forum."

Best regards, Rainer.

Translated on 22-10-2026, 1:09.

0.68V and 4.3V

Translated on 22-10-2026, 1:10.

chli1976 wrote:

I also had a fault code related to the fuel shut-off valve, a mechanical error. Unfortunately, I didn't save it, and I no longer know the error code.

You already have a problem there. When a problem is detected here, you're experiencing the exact emergency mode described. Just replace the valve and you're good to go.