O2 reading .3v when car is off normal?

[NateMR2]

I thought the signal wire wasnt suposto have voltage but even with no sensor it reads .3 v i bought a new one i was going to install but dont want to ruin it if its not suposto be supplied with voltage. The reason for this is my car is running rich as f on idle after warm up like 10.1 on the wide band tested my old sensor didnt seem to be working s13 rb25det

[Kingtal0n]

if you disconnect the O2 sensor narrowband, the engine should still run fine (nearly correct A/F ratio). If it does not, you need to pressure test for leaks.


Don't worry what voltage comes out of the ECU. Just make sure you use the correct wire (O2 signal) for the ecu input (signal).