I recently tuned my buddies GMC Sierra.
All was good for a few days, then it came back to me with 2 rear O2 sensor high voltage codes. I simply disabled the SEL checks as soon the cats are going to be gone. However now I noticed whèn logging the truck, as soon as it hits PE OR I force Open Loop with a small load, Bank number 1's O2 MV hits the floor, 60-70MV (lean) and stays there until it goes back into Closed Loop.
The other is reporting ~890 MV as it should. WBO2 confirms that this is correct with one bank at1 15.3 AFR, and the other bank at 12.5 AFR. No misfires are being reported. So..... would you guys say that the cats are plugging/plugged or something else is going on?
Thanks for any input.