PCM/Oxygen Sensor - Help Please

My '97 Sable is displaying codes P0420 and P0430. I would like to determine if I have a problem with the O2 sensors, the convertors or a wiring problem.

I tried to use the diagnostic procedure mentioned in the Haynes manual. Basically, it said to connect a multimeter to a good ground, backprobe the O2 sensor connector and turn the ignition to the ON position. It said that the reading should be .4 volts or 400 millivolts. I am not getting this reading or anything close to it. My questions are these:


Which wire should I be probing? What color is it coming out of the wiring harness?

Could I have a wiring problem and if so could it cause these codes to be displayed? There seems to be one common wire running between all 4 O2 sensors, some other sensors and the PCM. How can I effectively test this wire for proper operation?

Does anyone know how to measure the O2 sensor related terminals at the PCM for proper signal/voltage? I saw a wiring diagram in the back of the Haynes manual which points out the various O2 related wires , but doesn't tell you how to test the PCM for proper output/input?


Any and all assistance would be appreciated.

Thanks.

Frank

My '97 Sable is displaying codes P0420 and P0430. I would like to determine if I have a problem with the O2 sensors, the convertors or a wiring problem.

I tried to use the diagnostic procedure mentioned in the Haynes manual. Basically, it said to connect a multimeter to a good ground, backprobe the O2 sensor connector and turn the ignition to the ON position. It said that the reading should be .4 volts or 400 millivolts. I am not getting this reading or anything close to it. My questions are these:


Which wire should I be probing? What color is it coming out of the wiring harness?

Could I have a wiring problem and if so could it cause these codes to be displayed? There seems to be one common wire running between all 4 O2 sensors, some other sensors and the PCM. How can I effectively test this wire for proper operation?

Does anyone know how to measure the O2 sensor related terminals at the PCM for proper signal/voltage? I saw a wiring diagram in the back of the Haynes manual which points out the various O2 related wires , but doesn't tell you how to test the PCM for proper output/input?


Any and all assistance would be appreciated.

Thanks.

Frank

LoL, Im wondering the same. Car is starting to run a bit rough, I think I have slipped on the maitenance in that specific area(o2 sensor). Matter of fact, I dont even know where they are located at ? And truthfully, since there are 4 (2 up and 2 down), is it imperative to change all 4 of them? Or can you just change the 2 ? I was reading, and the a book says 2 affect the fuel ratio, the others do not, but do send feedback to the CPU. What for if not goin to influence, general Polls ?

Anways, as for the job of replacing, it, woudl I be better off paying some one to do this ? I was quoted at 550, and he said it could be higher depending on how many were bad. There is NO way in h*ll Im paying that much for anyone to R&R o2 sensors. Is the job that bad, or are they tryin to get me ? Ordinarilly on other cars its a standard 80 -100, and that seems a bit steep for a job like that. But never messed with one of these before. Anyone have an suggestions as to the difficulty and location of these puppies ? Its a 99.