Nor_Cal_Angler

Hey guys....

Background: P1291 about a week ago...cleared it...grid heaters cycle really fast and only a very flicker of the lights and volt drop....truck runs great but even after the truck is at operating temp I can be idling at a red light and hear the "click" and see a volt drop the very quickly back to normal and it just repeats this....

Solution: I checked old IAT, it wasnt dirty but I decided to replace the IAT this saturday (man that is a PITA but got it in) NO CODES UPON COMPLETION and drove the truck all day SUNDAY

This morning, I fire up the truck (kinda cold out, 40's) and then go inside, I come out and check engine is on and I notice no grid heater cycle...I havent checked codes...but I assume P1291....I will check them both with the KEY CYCLE and a SCANNER and get back to you all with the info..but I am pretty sure its GRID HEATER...

Whats next....RELAYS...or HEATER ELEMENT...(durring IAT replacement..I checked voltage before relay from power feed at battery...12V I checked voltage at heater element..12v...

My thoughts are the relays might be sticking open or triping getting ready to fail due to the "fast cycling" of heater element...

Am I on the right track????

NCA

johnh

the grid heater relay control wire connections are push on connectors and loosen over time, to tighten them up crimp lightly with a pair of pliers and push them back on .....you will feel the diffference

Nor_Cal_Angler

John,

Thanks

Are you refering to the Black/yellow, orange, etc etc...smaller wires that are on the bottom of the rely...I think they connect to the ECM??? I will check those smaller wires.

Jake

PS...Scan showed 1291...cleared it....but it is warm (er) out now...no return code.