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

[Boomer]

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]

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]

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]

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?

 

[grcauto]

I have NOT tried to read heater current. I wonder if freeze data when the code sets would help?

Read the current. Don't worry about the FF it will not help in this.

 

[nickb2]

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

 

[Boomer]

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.

 

[Boomer]

The P0135 is now the only code that is appearing. I checked it today for current draw. It's drawing about 700 milliamps. Pretty close to what I'd expect. I also repeated the headlight test and the light worked fine. It was drawing 3 amps. That's what it should draw given it's a 35 watt headlamp. I then checked for codes even though the light was not on. (I cleared the light the other day again) It had the P0135 and said "Intermittent" When I check it, it seems to be working fine.

 

[billr]

700 mA seems kind of low to me. Is there a similar sensor on the other bank you check, for comparison?

 

[Boomer]

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

Hey Nick, thanks for the vine buddy. As you can see, I'm still fighting this. I can't let it beat me!

 

[Boomer]

700 mA seems kind of low to me. Is there a similar sensor on the other bank you check, for comparison?

Slightly low if it's accurate. I think I earlier measured it's resistance at 13 ohms. 13/12 would leave it at just slight above 1 ohm. There is an identical sensor on the opposite side. It was acting up before so I hate to disturb it now that it's working fine. I do still have the original which had about the same resistance. Maybe I can throw it back in and see what happens.

 

[billr]

Another suggestion is to measure voltage to the heater, back-probing with the sensor connected; and compare that to what the similar one on the other side has. Point is, the sensor resistance is only part of the equation, wiring/connectors and any switches/relays also have to be considered.

Don't you have a clamp-on DC ammeter? You should be able to measure current on the other sensor without "disturbing" it. And, I gotta ask... what is the accuracy of that meter down at 1A?

 

[nickb2]

Found this link interesting, it even has pictures. (@Bill, see clamp on!, you rock)

Diagnosing O2 Sensor Heater Circuit Failures | MOTOR

As vehicles grow older, there comes a point when the oxygen or air/fuel ratio sensor’s heater circuit will probably fail. When that happens, the easiest fix is to install a new sensor. But when the vehicle comes back two days later with the same heater code, what then? A local shop called me in on …

www.motor.com

 

[nickb2]

Hey Nick, thanks for the vine buddy. As you can see, I'm still fighting this. I can't let it beat me!

Hope you not working to hard like I am. shyster.

 

[nickb2]

Dang it, my french mind loves this song.