1991 245 LH3.1 o2 sensor issues

[goofee691]

So my car is a 1991 volvo 245 with M47 transmission. It has LH3.1 and recently It started throwing a 2-1-2 code even though I had recently replaced the O2 sensor. I just replaced it with a non-generic one and I am still getting the 2-1-2 code after driving a mile or 2. I looked at the o2 with the engine running but the o2 not plugged in with a volt meter and am not seeing voltage on it. the green wire from the ECU is giving .45v and the engine does not react to being grounded or being pulled up to .9v

Anyone have a suggestion as to whats going on?

Thanks.

[goofee691]

Solved, found that the heating element for the o2 was not getting power. I looked at the fuse but never had checked for power at the fuse as I figured I would have a no run/start situation since the fuel pump is on the same fuse. Turns out the fuel pump relay was not function but I was still able to start and drive the car without any noticeable sluggishness. I did replace the pre-pump recently so maybe the new one was supplying enough pressure to operate the fuel injectors.

[mtd240]

Interesting. Thanks for posting the solution. Need to look at some wiring diagrams and see how you managed to drive the car with a failed fuel pump relay!