VW Passat 3B Lambda Sensor Voltage - ARM Engine

Hi there,

The SIMOS 2 module in this car measures 1.5V on the control unit side when the oxygen sensor is disconnected.

VCDS displays a voltage of 1.5V when the sensor is connected and cold, which drops to 1.2V when warm.
Since it's a standard oxygen sensor, I'm leaning towards a new or used control unit, as the target value here should be 0.5V?

Best regards, Michael.

Hello Michael,

Have you measured the reference voltage with a multimeter? Is the cable harness okay and undamaged?
Rarely, but sometimes, the control unit may provide incorrect values due to a diagnostic error, for example, when reading the internal resistance of my vehicle's battery from the onboard network control unit (due to a software bug).

See:
http://www.bosch-lambdasonde.de/de/downloads/bosch_tipps_lamdasonden.pdf

Best regards, Rainer.

Hello Rainer,

mdonau wrote:

The SIMOS 2 module in this car measures 1.5V on the control unit side when the oxygen sensor is disconnected.

On-site measurement using a multimeter (the traditional method).
I thought that would be clear when I wrote about the plug side .

The distance from the engine control unit (STG) to the connector is only about 30 cm, and everything appears normal; it's still well-wrapped.
I could, of course, also measure it directly at the STG (Selective Torque Generator).
But since both VCDS and the multimeter show the same value, it could only be due to an external voltage source.
It's likely an internal error within the control unit (ECU), especially because the voltage changes during the warm-up phase.

Best regards, Michael.

EDIT: I temporarily opened the engine control unit (ECU) for testing purposes, but didn't see anything obvious, and changing the temperature didn't make any difference.

Quote:

I thought that would be clear when I wrote about the plug side

.
Based on my understanding of the control unit's perspective, I interpreted that the value originated from the control unit itself, meaning it was measured using a diagnostic tool.

Okay, if the multimeter and VCDS are saying the same thing, then the value does seem strange.

Quote:

Measuring the reference voltage. Guidelines: 400...500 mV Check the control unit/electrical system. Measurement at the separated connector. connection on the control unit side. to carry out.

Quote:

I could, of course, also measure it directly at the STG.

Okay, please temporarily supply the engine control unit with +12V, ground, etc., and check that.


Is it possible to get a clear picture of the control unit circuit board, showing the components?

Best regards, Rainer.

Hi Rainer,
Further testing is performed, with the probe connected, and the reading is always 1.5V.
Even with disconnected connectors and a direct +12V and ground connection from the battery to the control unit, the voltage between the two contacts remains the same.

I suppose I'll have to find a different ECU for her then.

Best regards, Michael.

You shouldn't try to revive dead horses.

Engine started with a new control unit, but still the same dirt/mess .
Endless maintenance issues, consumes 1 liter of oil every 1000 km, time to contact the press.

Shortly after starting, I heard a backfire (a spark?).
I suspect something might be wrong and that it immediately killed the new ECU (Engine Control Unit).

Is the cable from the control unit to the oxygen sensor really okay?

Best regards, Rainer.

Hi,

did anything else come out here? The lambda reference potential is an interesting topic .

Best regards,

January.

No, that engine wasn't worth any more effort.

When candles become excessively carbonized due to oil, there is a very high probability that the oxygen sensor is also faulty .