Can you tell me why oxygen sensors dont read? (447 mV flat line) / doesnt go into CL?

[GrannySShifting]

Oxygen sensors plugged in, brand new Fbody, brand new DBC harness from PSI in NJ, no extensions, heater circuit has power and ground, sensor gets hot key on engine off, purple and tan wires are in 26/66 and 29/69 like they are supposed to be and continuity test checks out, but always reads stagnant 447-449 mV.

I can use open loop target A/F to drive the car stumbling rich to misfiring lean and the voltage readings dont change. How is the PCM no seeing a different voltage?

Also even up to 180F running the closed loop status bit never changes when the Closed Loop Enable is at 100 or so degrees?

Found customer had one of the cylinder head grounds not on at first, but still acts the same after finding that

[mowton]

You have MAF Hi fail at 0, this will fail over to SD (VE table). You also have P0101-0103 as no Mil. Is there a MAF in this Setup or are you tuning in Speed Density?

Update -- I got it, Custom OS 1 Bar speed density........

Ed M

[truckshop]

That's what it reads when the circuit is open. Make sure your wiring is correct.

[POWERZONE]

Are these brand new O2 sensors? If so what brand?

[WS6FirebirdTA00]

Check the wiring harness pinout at the o2 sensor. I have had problems in the past with miswired connectors.

[GrannySShifting]

Yes brand new, and yes it looks like they are open, but the wiring checks out. Heater circuit on C and D, hih low signals on A-B like I said in first post continuity checks everything tests ok

[aknovaman]

Measure heater voltage at O2 sensor connectors.

[IronBird]

Did anybody solve this yet? I have the same issue.

[kevin87turbot]

Did anybody solve this yet? I have the same issue.

It's typically just bad O2 sensors or faulty wiring.

[GrannySShifting]

It's typically just bad O2 sensors or faulty wiring.

Yeah it usually is, I cannot remember for the life of me what this particular cars issue, but it was really wierd

[TheMechanic]

Do the diag. Get out the voltmeter. Test for O2 sensor voltage using min max. If you have a good swing than just grab a wire from the positive battery down to the pigtail. Lick your fingers and put the live 12 v in one hand and the sensor return in the other. Should get a good 1.0 volt on the scan tool.

[GHuggins]

Did this just start? Such as after a recent flash or anything like that? Has it been flashed with SCT at any point? SCT seems to cause dead perfectly good O2 issues more than anything else. Corrupted tune files will also do it. You may even notice idle issues or idle tuning issues. The best solution is to find another OS you can swap out of another OE file from the repository then copy over your tune changes into it. Do a write entire, make sure the problem is gone then continue. Seen this several times in the last 3ish months just with files getting corrupted. First saw it about 5ish years ago going in behind a sct device. This is of course after making sure all of your voltages and what nots are there

Then really stupid thing to check - make sure your tune is setup to run in closed loop and something didn't get fat fingered

[IronBird]

I found the issue with mine. The sensors were too far downstream and they weren’t getting hot enough. I switched to sensors with higher wattage heaters and it’s all good.

[TheMechanic]

I found the issue with mine. The sensors were too far downstream and they weren’t getting hot enough. I switched to sensors with higher wattage heaters and it’s all good.

That begs the question. How did you find "higher wattage" HO2S's? How did you determine they are higher wattage?

Ok so the last part about determining wattage should be easy enough with a current meter, but still I have NEVER heard of a manufacturer mention the wattage/current of their heater circuit.

[blindsquirrel]

Something smells funny about that.

[GrannySShifting]

Yes same question lol

[blindsquirrel]

And most of them control the heaters with PWM anyway, so it will command whatever duty cycle is needed to reach a calculated temperature, so the 'power' of the heater element is very nearly completely irrelevant.

[IronBird]

I read that Bosch 13111 sensors have higher wattage heaters. It solved the problem temporarily, but now I’m getting the slow response codes again so it’s back to troubleshooting.

[IronBird]

And most of them control the heaters with PWM anyway, so it will command whatever duty cycle is needed to reach a calculated temperature, so the 'power' of the heater element is very nearly completely irrelevant.

Wouldn’t this require a sensor temperature feedback to the ECM? I’ve never seen that in the wiring diagrams.

[gtstorey]

Wouldn’t this require a sensor temperature feedback to the ECM? I’ve never seen that in the wiring diagrams.

Calculated not measured. Using engine parameters to guess what the o2 heater needs to do.