Low voltage to O2 sens

[Drifter60060]

I have a 97 GMC Sierra with 5.0. My truck doesn't have most of the luxury options such as power windows, power locks, power seats. All it has extra is cruise. I keep getting an SES light (P0137). I checked the voltages at the left bank sens 2 (I assume this is driver side downstream O2) using the purple and tan wires. I have low voltage there, only getting about .386 mV, manual says it should be between .400 and .450. I have 11.8v on the pink wire.

So here's my question: can I make a jumper from the passenger side post cat sensor? I don't know the pin locations on the PCM to check my voltage there, so my only options are to make jumper wires or live with the SES light. By the way, I know both of my post cat sensors are good, so that's not the problem.

 

This thing is kickin my butt. I don't want to have to buy a new PCM. Thanks for any help in advance.

[sleepur606]

Is the SES emissions related? You have a 97 so it should be ODBII...

 

Before you condemn the PCM, can I ask a question? What kind of meter are you using to check the voltage on output...the spot where you're getting .386 mV. If you're using a volt meter that has an average function, looks like a triangle or delta, it will tell you the min/max/avg readings from the O2 sensor. If everything is low, including max and min, then it could be an O2 sensor problem, a lot less costly than the PCM. Best way to confirm an O2 sensor problem is if the readings are either high or low, but you have normal emissions readings. I know not everyone has a 4 Gas Analyzer at their disposal, but a lot of local schools or vocational schools may be willing to test the truck for you. Sorry I can't offer anything certain.

[03silverado]

are you sure you don't have a exhaust leak on the driver side? the leak would have to be after the front sensor but before the post cat sensor. if there is an exhaust leak between those points you will have low voltage output from the post cat sensor.