PO155 2002 Chevy S10 4x4 4.3L 176,000 miles

Boomer

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Agreed. it is likely that the O2 sensors are not powered up when engine is not running.

If you still get no voltage at S101 when the engine is running, go back to C2 pin 74 on the PCM itself. Open up the PCM and read voltage right at the pin that is soldered to the PCB. Also, will be a good opportunity to do a visual check for poor solder connections on the PCB...
That would be a good idea. The screws holding the metal case together must be on the bottom because looking at it, I don’t see any.
 

Boomer

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Perhaps the PCM only powers up the O2 heaters when the engine is actually running?
Well, I checked the truck out today and, you're right Dan. The wire got hot when I started the engine. I was checking at the splice. I also checked the ground side coming from the PCM and it was fine. I then went down to the front sensor connector on the passenger side and opened the connector. I connected an H4656 headlight to the power and ground wires. The light is rated at 35W so at 12 volts that should have been drawing almost 3 amps. The light shined just fine. I can't see any reason the new Bosch sensors wouldn't be heating just fine. I'm beginning to wonder if it isn't an intermittent problem? Seems like the light comes back on pretty quickly though. I cleared it today. I will see and take note of when it comes back on.
 

billr

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Way back, in reply #11, you reported that you have a clamp-on DC ammeter. Have you tried using that to read actual heater current?

Unfortunately, if this is an intermittent problem, you will probably have to leave a meter connected all the time for frequent checking. An in-line ammeter would be better for that, I think. Better yet, and some way to do data-logging; but that would take some creativity and maybe special equipment
 

Boomer

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Way back, in reply #11, you reported that you have a clamp-on DC ammeter. Have you tried using that to read actual heater current?

Unfortunately, if this is an intermittent problem, you will probably have to leave a meter connected all the time for frequent checking. An in-line ammeter would be better for that, I think. Better yet, and some way to do data-logging; but that would take some creativity and maybe special equipment
I have NOT tried to read heater current. I wonder if freeze data when the code sets would help?
 

nickb2

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Way late to game, but yeah, FF is of no use here. Some scanners will give amp / current draw, but not your actron thing. Sorry.

Also need A SCOPE, cuz actually reading that with a clamp on will only give a low resolution.

Ok, bye bye, I just did a dash in and out.

BTW, hi boomer, long time no speak. PM if you want ;) :bat:
 

Boomer

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Update: I had to work 8 12 hour days in a row so I haven't messed with it. I did however notice that I kept clearing the light and the only code that kept coming back now is the P0135. That for the record is the side I did NOT mess with in post 32. The front passenger side code hasn't returned since. Yesterday I decided to check the driver side. I did the same as the other. I hooked a headlight up to the GRN/WHT and GRN wires. The headlight worked fine. For now I will see on the next couple of highway trips (one will be today) if the codes from either one come back.
 
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