B1S1 going to -38% and +50%. B2S1 acting normal

[cjsgarage]

Thought I posted this, but maybe my laptop died and I forgot. Who knows?

I have had it on two cars in a row now. One Gen III 6.0 LQ9 with an ASA cam. Os is a 2001 Yukon Denali. Tried replacing O2 sensor, as it was original. Not much change. Verified wiring is good with ohmmeter. Still getting basically no change in B1S1 fuel trims. Not sure why.

The other car is a 5.3 with a GM hot cam with a Magnuson blower on it running a 2 Bar OS. 2001 Silverado OS. Doing the same thing.

Anyone have any experience with this? A heater not working? A bad ground for a sensor? Possibly a sensor without case ground and it needed it? One of these cars is wired with a redundant case ground set up. One has got a case grounded O2 set up (looks like a 2500 sensor).


If you drive it for a bit, or are hard on it (make a pull) it might switch from -38% STFT to +50.3% STFT.

Anyone?

I?ll attach logs when my laptop boots up.

[cjsgarage]

I did try new O2s in the Silverado OS car, also. Also put a new fuel pump in it and I’m going to try injectors. I can’t give these cars back the fuel control cause it makes them sluggish. I don’t want to leave them in OpenLoop. And theories or moonshots are welcome.

[blindsquirrel]

If you cross the B1/B2 wiring it'll do that exact thing. PCM tries to correct fuel on the bank that sensor isn't reading and it freaks out.

[Ben Charles]

Swapped 02 sensors.. if not then you have much bigger problems

[cjsgarage]

If you cross the B1/B2 wiring it'll do that exact thing. PCM tries to correct fuel on the bank that sensor isn't reading and it freaks out.

Yep. I?m aware of this. I?m 99.99% sure neither applies.

The 5.3 ran perfect before it got the blower. Then it spent time at a paint shop. And now it?s acting strange.

The 6.0 I did rebuild the entire harness on, so that the harness would be pretty. But I have verified the pinouts with an ohmmeter. And B2 is super normal.

Usually they end up opposing each other because they command one way and act another and it compounds until they?re maxed out.

But this doesn?t seem that way.

I will recheck them both just to be sure B1 is pinned to B1 and B2 is pinned into B2. Just to eliminate it.

[cjsgarage]

I have swapped O2s. Not on the 6.0. But the 5.3 I have. And things changed. But I put new O2 sensors in both sides of the 5.3L.