P0178 on P01 flex swap, content stuck at default %

[Gutless]

I installed a flex sensor on my G body LS swap car over the winter and am not getting flex content to read in the PCM.

I have an 01 Denali DBW harness running a LS2 silver TB on an lq4 with a t56. I previously had an 01 p01 PCM that was not flex compatible so I purchased an 02 tahoe factory flex PCM and did the 2 BAR SD enhancement on it and copied all my non flex related parts of the tune from the previous 01 PCM to the new 02 PCM.

I have confirmed half a dozen times that I have power and ground to the correct pins at the flex sensor and that I have continuity from the signal out pin at the sensor to the correct pin on the PCM.

The sensor and plug was brand new from Pace in February. When I hook up my DMM between the signal wire (I depinned it from the PCM plug to check) and ground to check the sensor is outputting 50-150 hz, I get jibberish (1-4k hz) I have never had good luck reading frequency with a DMM and don't have easy access to an oscilloscope.

I get a P0178 DTC Fuel Composition Sensor Circuit Low Frequency and the scanner is stuck at 37.6%, or close enough to the default of 40%.

Is this enough evidence to claim a defective flex sensor? It is a new part from a reputable sensor and most errors with these sensors are non flex compatible tune or wrong wiring, and I know both are correct. I fundamentally can't convince myself to throw parts at it.

I attached the tune and screenshot of what I get in the scanner.

Thoughts?

SS1.png
86GP 5-22-20 Flex.hpt

[Gutless]

Oh in case anyone ever has this problem in the future, it turned out to be the damn signal wire going from the flex sensor to the PCM. I ran a new wire from the sensor to the PCM and finally got signal.

I tried saving myself 5 minutes when I installed the sensor and reused the passenger rear 02 wiring for ground, power, and signal. Even though I had continuity to the PCM and no signs the wire was bad, it was somehow introducing noise in the signal and 50hz went in the wire at the sensor and 5khz went out at the PCM.

In order to bench test a flex sensor with an oscilloscope or DMM you need a 2K pullup resistor between signal and voltage supply. I ordered a second sensor and went down the rabbit hole of bad sensors for a while. You can't just hook it up not to the PCM and hope to read it with a DMM without that resistor.

I probably have 80 hours diagnosing this and it took 6 months on and off.

If you search the gargler for info and find nothing (like I did) the sensor is probably fine even though its throwing a 'sensor bad' code. Run a new wire from the sensor to the PCM and give it a shot. Even if the wires have continuity, aren't shorted, there might be something funcky going on.