Hello:

My 411 application to my 350 Chevelle is running but I can't read the front O2 sensors. Both read ~450mV and fluctuate by a few mV. The engine starts and is driveable, just open loop. I can read engine temp, IAT, maf, map, rpm, spark advance, vss, and I hooked up the single wire prndl. I swapped the coil and injector wires for the gen 1 firing order and reassigned the cylinders to the O2 banks. The only thing not hooked up are the knock sensors. It runs rich and I can smell it. Took it on a drive and it runs great. It is more powerful than TPI: more responsive and more powerful. Idles a little rough especially after startup and gets smoother warmed up.

Plugging on a spare O2 sensor connector (chopped from an old O2 sensor) I was able to confirm 12V and good ground wires to the heater. Both sensors get warm to touch after two min so the heaters are working. Heater 12V and ground are hard wired and not controlled by the PCM. The two sensor wires go to the PCM blue connector pins: B1 S1 -PPL/Wht 69, +Tan/Wht 29. I ohmed the wires from the cutoff connector back to the blue connector pins and had good continuity. I grounded both 69 and 29 and reading didn't change, still fluctuating around 450mV. Jumped 69 and 29 together and reading didn't change. I didn't apply voltage since it's a low voltage circuit. The O2 sensor acts like a battery varying it's voltage to the PCM. The PCM is supposed to be like a voltmeter reading the O2 sensor. Tieing the 69 and 29 wires together should make near 0mV. This is the part that makes me question the PCM functionality.

I'm wondering if there is a setting in the bin to make the PCM read the voltages for 69 and 29? It seems like it should be something simple. The same thing happens on Bank 2.

I have a 2nd 411 PCM loaded with the same OS and bin. Same behavior. So what else is it: sensor, harness, and PCM eliminated?

I'm using an AVT 852 cable and AVT LS1 DPID V1.06-aldldroid.adx with tunerpro5.

Maybe someone went through this and knows the answer. Searching found the same issue but no root cause with others. Maybe this write-up can be a reference for others.

Take care,

TPIChevelle