I replaced my oil pressure sending unit this morning, now am getting Knock Sensor 1 and Knock sensor 2 Circuit Low Input. Is there a plug on the rear of the intake that the harness plugs into the knock sensors ( I see they are under the intake, didn't even know that till I got the code and started researching this). Possibly pulled the plug that goes to the knock sensors from external of the motor while getting my hand between firewall and motor to replace oil pressure sending unit? I know I didn't unclip any other harness plugs, I'd of thought it'd have a clip to keep it plugged in like other harness connectors do... does this (assuming this connection is back there and exists) one not?

 

The knock sensor harness comes out the lower back of the intake and loops around to connect up on the upper back top of the intake. This is a pic I found online for a GM truck - its the same on our H2 Hummers. You will need to to pull the top beauty cover off to get to the connector. Sounds like you might have somehow disconnected it when you did the oil pressure sender.

 

I figured out where it plugged in shortly after posting my original post. It was connected so figured I must have pushed and tugged on the harness hard enough trying to get my hand to the oil pressure sensor that I damaged the harness under the intake somehow. I pulled the intake. One sensor looks reasonably new, one was corroded bad, replaced the corroded one and put on a new harness, the connectors on the harness were old and brittle and crumbled when removing them from sensors so I really thought this was the problem. Put it all back together, cleared the codes, drove it a bit and the code came right back. I'm at a loss, it's has to not be getting a signal from both bank 1 and bank 2 cause it continues to get both codes low voltage from bank 1 and bank 2. All I can think is a wires in the main harness somewhere but that's a job I dont want to tackle tracing them all the way back to the computer or wherever they run to. I'm kind of stumped.

 

Hmmm.... that is odd to have both throwing codes. One other thing I shoudl have mentioned - hope you replaced the one knock sensor with a genuine ACDelco one. The aftermarket ones are garbage and generally fail in under a year. Then it gets fun - when you try to remove a generic one the casing comes apart and it just spins. I know this from firsthand experience.

But yes - there is something else somewhere causing the problems. Too coincidental that it only started after you changed the oil sensor. Something else got tugged on and pulled an connector apart or pinched the wires somewhere.