Alright guys I haven't been on here for a long time hoping for some help. My 04 cavalier with 92k threw a code for p0135 02 sensor b1s1 heater circuit failure. Figuring my miles i went out and bought an ac delco 02 cleared the code drove the car 20 mins later lights back. I have the same code. So does any one have a flow chart and some specs to test the circuit? I am hard pressed to believe I have a bad new sensor. Only other issue I have with the car is my digital odometer is not back light anymore about 3 months back the back light went out. so with my headlights on I can't see the odometer at all and with them off it is very faint. I have an aftermarket radio in but that's been in since the car had 8 miles on it.
Thanks guys for any help you can give me.
Theo.

Dont rule out getting a bad new part. Happens more than you'd think. As far as the back light, can you reach the back of it under the dash and see if it has a replaceable bulb? I'll bet it does. Its probably one of the twist sockets with a push in tab style bulb like a marker bulb.