Pontiac Repair: dont wanna rplace is im not sure, grand prix 3, best bet

Question
I got a 2003 grand prix 3.1 liter with. A p0135 which isthe xygen sensorr in the exhaust manifold I tested it it fluctuated under two hundred mv and over eighthundred mv do u think its the heater circuit whats my best bet I got sunday the sebenth to do it pplease help

Answer
Hi chris:

Those #'s are a good sweep for the sensor so it appears that it is working. Did you use a scan tool to read it or a volt meter? depending on how it's equipped it may have a computer driver heater ckt meaning the heater ckt is driven by the computer. on the older cars the heater is one any time the key is in the run position. on the older one it was easy to check the heater ckt/O2 you could just turn the key on and with in 20 minutes the 02 reading should drop below 100MV on the computer driven heaters the engine has to be running for the heater to work and that way  you can't see it working. But you can use a test light across the 2 wires for the heater and see if the light lighst when the car starts running if so then the heater is bad. Do this on a COLD engine on a hot restart the heater may or may not turn on. good luck :)