I just tried this on my car :

1. Cold engine, ignition on, not started voltage across 02 sensors about 0.3v

2. Engine started, voltage starts to move up and down, eventually cycling two or three times a second from about 0.2 to about 0.9 volts

3. Engine stopped, ignition on [engine a bit warm] voltage across o2 sensors about 0.03 volts

4. Allowed engine to cool for 15 minutes, voltage across 02 sensors back at 0.3

I hope this info is of some use.

It is hard to think of anything that could affect both sensors and both computers in exactly the same way.


Could it be that you have the wrong sensors, or have them somehow connected wrong ?

When I changed my sensors last the correct Bosch part no was 0 258 003 957 - 760

When I have had o2 sensors inactive it doesn't make the car run especially rich. Have you tried running it with the sensors disconnected.

Sorry, can't think of anything else, let us know how you get on.