So if I've verified I have power/continuity to/from C3-8 (1/1 O2 sensor heater control), and I've verified continuity to/from C1-4 (O2 sensor ground), what would be the next step? Checking to see if there is the correct voltage readings on C1-24 (1/1 O2 sensor signal) during engine operation? I'll also spray some electronics cleaner on the connector/harness for the sensor, but besides that what would be the best approach here?

 

Heater circuit is entirely separate from the signal circuit. Your issue is with the heater circuit. I would check resistance of the wires as well.... continuity doesn't account for that. If the wire is high resistance, for whatever reason, voltage drops.

 

I second this! I am chasing an electrical gremlin as well, I was checking resistance on wire after wire and all were near 1 ohm, then I hit one that was 30 ohms, so I had to find out why that one wire was different. You may find the same thing, high resistance will definitely cause problems.

 

Check resistance of all of the wires leading from the PCM to the 1/1 O2 sensor connector? Or just the heater wire? Also the voltage supplied by the PCM is supposed to be 12v correct?

 

Were you able to find out why the resistance was higher?

 

Supply voltage is 12 volts, yes, but, it comes from the PDC, not the PCM. PCM only controls/monitors the ground side of the circuit. Really only need to test the heater circuit wire.

 

So I tried testing the resistance while under the vehicle and my girlfriend checking the multimeter, supposedly the multimeter just read "OL" (open loop) when testing at O2 1/1. I verified continuity between the harness at the sensor and the connector at the PCM last week so I'm not sure what's up, gonna try again this evening just doing it solo to remove any possibility of user error.

 

Not yet, weather hasn't been very cooperative (truck wont fit in my shop, misses clearance by 2") but based on my research of the factory service manual and the wiring diagrams, I'm thinking the circuit in question hits a solenoid or sensor somewhere mid loop. Other things I'm looking for include corroded connections, bad splices, and less likely, but still possible, breaks to the wire inside the jacket. I do that by wiggling/shaking/bending the wire or even gently tugging on it while watching my resistance readings, they should stay pretty consistent unless you have a break or you accidentally knock one of your meter probes loose.

 

Sorry for the delay, was a busy week; so I now somehow have continuity on ALL O2 sensors from the connection to the sensor at the harness to C1-24 at the PCM which should only be for O2 1/1. All of the other sensor signal connections at the PCM (1/2 = C1-25, 2/1 = C1-26, and 2/2 = C1-29) do not have continuity. I also verified all sensors are grounding at C3-4. This was all done with the truck off and battery unplugged if that matters, don’t think it does since I’m just testing if there’s a connection between the sources on the wire.

At this rate I’m guessing have some electrical short somewhere…? which, if it’s the case, would be odd I’m not getting really bad performance or more engine codes since if my understanding is correct, it appears ALL O2s are shorting to the 1/1 signal wire?

 

Wrong wires..... You want to test the heater circuits, that's what your code is for..... So, 1/1 is Brown/violet wire at the O2 connector to C3, 8, 1/2 is Brown/white wire at the sensor, to C3, 16....