P0054 code help

[Henney]

I'm getting a P0054 and P0060 rear O2 sensor code in my 2005 LQ4 swap. I'm using a PSI harness and bought new AC Delco O2 sensors because the originals didn't match the harness plug. I did get the part number PSI recommended for the sensors. For exhaust, if it matters, I'm running Sanderson headers, H pipe and no cats.

I reset the code yesterday and started the engine a few times then drove and didn't get a code. This morning the code was present on my drive to work. Reading around here and ls1tech I checked grounds and fuses and everything checked out. There also isn't a short in the wiring from rub and the connections are solid. I looked at the freeze data from yesterday and today. Most of the numbers don't mean anything to me but I did notice in both cases the fluid temp was at ambient temp and the speed was 0, which to me says it's happening at first startup when the engine is cold.

So what's my next step? What actually happens within the ECM without the O2 sensor input? If the sensors work intermittently does the ECM use the data when it's available?

[ls1nova71]

Just curious, but why are you running post cat O2's? Also, running them with no cats will cause the DTC to set. I assume youre not running a full emmission swap since you dont have rear cats, so I would have that tuned out and do away with the rear O2's.

[BR3W CITY]

OP's post says he's running headers and no cats. If thats the case, then ya the rear o2's will always set a code.

[Henney]

So if I’m understanding you guys right I have the front O2 sensors installed and the rear O2 sensors deleted but with my ECM the rears weren’t removed and therefore it’s throwing the code. The statement below is from the PSI wiring harness instructions. I only have 2 O2 sensors not 4 so…

Factory Stock Vortec Engines utilized four (4) O2 Sensors; two (2) Sensors on each side of the engine, one before and one after the catalytic converter. The rear O2 Sensors (after the catalytic converters) are not used with the PSI Harness. Provisions are provided for two oxygen sensors in the harness. (SEE TABLE 2 FOR SENSOR PART NUMBERS)

[Henney]

Just to add, I had my ECM flashed by Frost and I'm pretty confident he removed the rear O2s.

[BR3W CITY]

Your codes are rear 02 failure, so that means that the ECM is looking for the rear 02's.

If no sensor is installed in the rear position (most of us aren't using them), then the ECM needs to have the input from those sensors ignored or "turned off". If those DTC's aren't turned off, then you will pop those codes every time. There really aren't other things that will cause a false DTC for the rear 02's.

[Henney]

Thank you