DTC P0156 & P0161 (continued...)

[vvansant]

Okay, I started a post about these codes a few days ago but it appears to have expired. Nevertheless, to summarize again my 96 GT is throwing the above 2 codes for sensor 2 bank 2. I have replaced O2 sensors (several times), installed MIL eliminators, and ruled out exhaust leaks. According to a few of you who posted, these codes point to more of a grounding issue of some kind. A summary of these codes is as follows:

P0156 - Oxygen Sensor Circuit (Bank 2 Sensor 2) Received from PCM
P0161 - Oxygen Sensor Heater Circuit (Bank 2 Sensor 2) Received from PCM

I did a visual inspection of my wiring harness from the O2 sensors up to where it connects in the engine bay. Everything looked good, no exposed wires, crossed pins, dirty connectors, anything grounded to the wiring, etc. I ran a KOER test and the PCM threw code P1127, "Heated Oxygen Sensor Heater not on During Test".

I am curious if anyone has any suggestions on what else to check? I did run some tests using a scanning tool but don't understand the parameters enough to provide valuable troubleshooting (e.g., SHRTFT_1_3, LONGFT_2_4, etc). I assume that the wiring I inspected up to the engine compartment gets to the PCM somehow but I'm not sure where. Does anyone know where I can find the wiring and PCM? Could this be a PCM issue? I am seriously considering finding one on eBay or at a local salvage yard just to rule it out. Could it be a grounding problem somewhere outside of the O2 wiring? I am at wits end on this.

 

[Mike97gt]

You have a new sensor in there right?

Do you run any sort of MIL elims?

If the sensor is new and no elims then it's really only two things the wiring or the PCM. You can try running brand new wires from the pcm down to the sensor itself

Sure it might be the PCM but I would be surprised, you need to check that wiring really good and run a conitnuity check on it.

 

[vvansant]

I suppose you're right, I will have to figure out the best way to test the continuity of those wires. I'm going to pickup a Hayes manual with the electrical specs though to help me out.

Here's another question, do I have to remove the MIL eliminators when I take the vehicle in for emission inspection? I ask b/c when I was running diagnostics on the other day both rear sensors were flatlined which means the PCM doesn't read them at all? I wonder what that will do to their readers?

 

[Mike97gt]

I suppose you're right, I will have to figure out the best way to test the continuity of those wires. I'm going to pickup a Hayes manual with the electrical specs though to help me out.

Here's another question, do I have to remove the MIL eliminators when I take the vehicle in for emission inspection? I ask b/c when I was running diagnostics on the other day both rear sensors were flatlined which means the PCM doesn't read them at all? I wonder what that will do to their readers?

All they test during emissions inspection is if the OBD2 monitors are ready and if there is no codes. They do not monitor pid data at all so you can leave them on.