No STFT readings

[r768]

2002 z06. I have no STFT readings with the HP scanner from either for the upstream O2 sensors. I will get P0134 and P0154 after driving about 10 to 15 miles. Cleared codes and repeated several times with same result. I have tried many of the suggestion found searching the forum with no success.
I have a MPVI without the wideband O2 option that a purchased to setup new injectors in my Chevy truck but have not done any tuning otherwise. I plan to purchase the upgraded version with the wideband next but would like to get this issue resolved first. Any help or suggestions will be most appreciated.
Tests performed for the upstream sensors. Checked and tested the o2 sensor signal and heater circuits. Heater has 12+volts with heater ground and chassis ground. Signal circuits have around .450v at both sensors when unplugged.
The HP scanner channel shows voltage for both sensors fluctuating around .450v, but the STFTs remain at 0.00% and never show a change.
Tested the hi and low circuits for continuity from the PCM to the sensors and no open or shorted circuits were detected.
Back probed the sensor wires and at the sensors and at the PCM and have .027 volts key on engine off after sensors heat up. At idle the readings fluctuate to over .350 when I revved the engine and jumped out to read the meter.
The HP scanner shows no changes with the sensors connected or disconnected. Shorting the sensor wires to ground had no effect on the reading.
Also tried the old sensors. Heated with a torch and sprayed brake clean. These test sensors when disconnected showed voltage readings close to 1 volt on a meter, same test connected showed no changes on the HP scanner.
History: I?ve had the car 2 years and blew the engine up last fall that included rods out the side, oil on the exhaust and flames out the left front wheel well and rear of the car. Current repairs included finding a LS6 core, complete rebuild including close to stock forged pistons and rods, stock heads rebuilt with ss valves, Scoggin Dickey very mild cam and Johnson lifters. While the engine was out, removed engine bay wiring harnesses and PCM. Repaired all damaged and burnt wires and checked and resistance tested each wire. All 4 O2 sensors were also replaced.

Thanks,

2023-07-24 2 IDLE.hpl2023-07-24 z06 Read 10.hpt

[5FDP]

The tune has the open loop STFT disabled.

Just click your open loop tab and you'll see it.

Also you can re-poll for supported parameters to make sure they are be polled for data. I can't view the log, so that as much as I can say for now.

[r768]

Thanks for the reply. attached is another log file from a few days ago. I have tried both disabled and enable setting for the STFT with no change. I have also re-polled several times. I do not have access to a different scan tool at the moment to see if PCM is seeing the O2 sensors. Since I am getting the P0134 and P0154 fault code I'm guessing not.

[blindsquirrel]

The codes are because the O2 sensors are not working, they never move from the default bias of 440-450mV. Diagnose the codes.

[r768]

The codes are because the O2 sensors are not working, they never move from the default bias of 440-450mV. Diagnose the codes.

Thanks, the O2 sensors are working and the signal is getting to the ECM wire pin. It seems that the signal is not recognized by the ECM or the scanner. I'm not sure this an HP Tuner issue, but i was hoping someone may have a suggestion or possible solution I could try.

[gtstorey]

BS is saying that if the o2 voltage is not changing from the voltage the ECM sees when they are unhooked. How do you know the o2 are working and the ECM is getting the signal? The only way I know of is from the o2 voltage.

[blindsquirrel]

450mV is what the PCM puts out on the O2 signal wires, called 'bias voltage'. It will read 450mV with no sensors plugged in. Reading that 450mV does not mean the signal is getting to the PCM, it means just the opposite.

[r768]

[QUOTE=blindsquirrel;739781]450mV is what the PCM puts out on the O2 signal wires, called 'bias voltage'. It will read 450mV with no sensors plugged in. Reading that 450mV does not mean the signal is getting to the PCM, it means just the opposite.[/QUOTE

Thanks and correct. I did back probe the PCM wires and after the O2 sensor heated up, the voltage would drop below 0.02v at idle. Reving the engine a little produced a momentary change of up to 0.80v then back down to 0.02v range. The car is currently up on jacks and these last tests where done in the garage.

[blindsquirrel]

So, are the O2 sensor high & sensor low wires going to the correct pins at the PCM connectors? C1 69 & 29 for B1S1, C1 26 & 66 for B2S1?

Verify that, then do a bypass test while the scanner's running. If the wires are going to the right pins, and the wires have good continuity from one end to the other, and by jumpering (or with a test light, if you're a scaredy cat) you can't drive the signal low, then drive the signal high, the only thing left is a defective PCM. I'd say it's probably unlikely that there would be a single internal failure that takes out only those signal pins all by themselves.

[r768]

Thanks for the reply, the sensor wires are connected to the pins as you described. I have run the tests as you described with no changes to the scanner reading. The voltmeter will respond as expected when back probing the PCM wire connectors. I fear that the PCM was damaged from the shorted wires as results of the fire, but I was hoping someone had a better solution. I would like to prove the PCM has failed before trying to source a new one. Just not sure of the best way to test for this failure.

[blindsquirrel]

I don't think there are any settings anywhere in the tune file that will make the O2s not report/display voltage. Not even if it's forced open loop and all the DTCs set to No Error, they will still show the voltage in the scanner.

So if it's not bad/unplugged sensors, and it's not cut wiring, and it's pinned correctly, and a bypass test won't show any change from the bias voltage, I don't think there is anything else left it could be other than PCM.

[r768]

Thanks, and I think you're right. I was just hoping someone would have a magic pill to make thinks like new. Any suggestions for a PCM sources?

[r768]

Thanks again for the help and responses. I decided to try a pair of seasoned sensors at the recommendations of a friend and the O2 sensors are responding as they should now and the scanner is logging info so I can start getting this new combo tuned in. Sure wish I wasn't so good at learning the hard way lol. Now I need to figure out what is wrong with those new sensors...

[blindsquirrel]

I'd want to be figuring out what went wrong when performing the bypass test that should have made the voltage change but didn't...