Hello all, I have a 1991 245 with the LH 2.4 injection. I had a rattling converter that stopped rattling and shortly thereafter the Check Engine Light came on. It gave me the code for a bad O2 sensor (1-2-1 or 2-1-2 can't remember at the moment) Anyway, I had a new converter put on and I installed a new Bosch O2 sensor. I cleared the code out and went driving. Within about 20 miles the CEL came on again. Once again it said it was a bad O2 sensor. I checked all the connection and cleared the code out again. It has now come on again and I am at a loss. I don't know if I should go buy another O2 sensor or what to do. The car did "buck" a few times shortly before the CEL came on. The last time it did that, it was the Mass Air Meter. It has been several years so I don't remember if it gave a fault code for the AMM or not. My mind is not what it was years ago. Any help or advise most welcome :)

Scott in Dallas

Check the fuse to make sure its tight in the holder and not building resistance to trip the light. Does it only come on once engine is warmed up.

No, it comes on the moment I start the car :(

Try clearing the code by momentarily removing fuse 6, instead of using the button pressing procedure. Then double check to see that fuse 4 is passing power (only when running now) and your tank pump is working. If you are still setting the code for O2 sensor, measure the voltage at the junction between the sensor cable and the engine harness (the green wire connects to a black wire under a rubber boot). Make sure it is 0.5V when you first turn the key on, but varies from that after you have the car running a minute.

Thanks for the reply Art. I can hear my pump in the tank working. I checked the single connector (green wire to black) and it does vary and go up and down etc. I checked the yellow/red and it has no voltage with just the key ON, but does have 13 volts or so when the car is running. The black wire in the double connector does have a good ground. I replaced the crummy Euro fuses on #4 and #6 with Blade type fuses as I'm sick and tired of fooling with them. Drove the car to work today and no code so far. Always seems to reappear on the way home for some reason :(

Scott in Dallas