Service 4wd Light

[jeepstud]

Ok here is the background. 2002 GMC Sierra with AutoTrac. 89,000 miles. To date have not had any Service 4WD lights.

 

Light came on and I went to the local AAMCO, they scanned it for free and found C0327 "Encoder Motor" fault. I had no lights on the dash and could not change to any T Case position. I also had no speedometer indication. I assume this is related.

 

I pulled he motor and replaced with a remanufactured unit from Advance Auto ($120 w/ coupon). I used a crecent wrench to line the T Case up into what I believed was 2HI. It lined up perfectly with the encoder motor and tightened it back down, plugged in the plugs and turned the key back to run. Same Deal service 4WD with no lights on the dash. I pulled the switch on the dash and inspected the solder joints on the backside, I didn't really see anything wrong. I touched each one with the soldering iron/solder anyway. Reinstalled the switch, still nothing. I cleaned the ground below the drivers seat, nothing. I will take the truck down to a local store with the switch but shouldnt the computer have thrown a different code for the switch?

 

I tried pulling the battery leads for 10 minutes hoping to cause a reset. Nothing. I tried pulling both the 4wd and the ATC fuse both with the ignition off and then on. Both times I let it sit for for a couple of minutes. No change still Service 4WD with no lights. Each time I plugged them in though I think I heard the front axle actuator moving. I heard something anyway.

 

I am getting ready to try a new switch anyway but it is beginning to feel a little bit like easter egging, I am replacing parts with no logical reason. Which leads me to this email.

 

Are there some electrical checks I can do at the various connectors to help narrow my problem down? A drawing I found on EBSCO shows an 8V reference coming from the TCSCM to pin E of the Encoder. I'll check that tomorrow. Any other meter checks someone reccomends?

 

Can the Snap on Tool reset this code?

 

I have also read about reprogramming? Is that something I should consider.

 

I usually can fix almost anything I run into and this one has got me really frustrated. I feel pretty helpless. Anybody with some experience narrowing this down?

[gmtech4]

holy crap, you've spent alot of money and time and the 327 code is for the sensor inside the encoder motor,you did that with a complete reman POS ..

 

what has to happen now is get the entire code diagnosed properly ,your out now ,your done ,either get a service manual thru alldata online or something ,but dont do anything else but have it done properly.

 

this one is for the holy shit file

 

a code for the switch is 1275 i think ,cant remember

 

good luck

[jeepstud]

Is the dealer the only place that can deal with it at this point? Can AAMCO? Man I hate going there . ..

 

Can that code be cleared causing a reset?

[gmtech4]

usually when a code is ran and passed the light will go out ,

 

causing a what ??? makes no sence

 

a tech with a brain can diag it with the proper diag tree and a scanner of some sort or

 

a dealer that knows them all to well ,

 

good luck again

[jeepstud]

does the fact that I have no speed indication give us any clues? Could a bad speed sensor throw the service 4wd light?

 

When I called the service department he mentioned ther was a way to "reset" the truck, possibly by shorting two wires together? He mentioned I ran the risk of locking up my stereo. Does anyone know what this procedure is?

 

TJK

[old-chevy-dude]

does the fact that I have no speed indication give us any clues? Could a bad speed sensor throw the service 4wd light?

 

When I called the service department he mentioned ther was a way to "reset" the truck, possibly by shorting two wires together? He mentioned I ran the risk of locking up my stereo. Does anyone know what this procedure is?

 

TJK

 

 

disconnect both battery cables.. the positive and the negative, while they are both OFF the battery, tap the wires together, this is "supposed" to short and force a reset of the computers.

 

as the battery cables are disconnected from the battery "in theory" what you are doing is clearing out any residual power left in the cables and computers.

 

I have done this and it has corrected issues with RFID ignition systems and park sense errors on Dodge vehicles, I can't speak for GM on the matter..

[jeepstud]

No luck with any type of reset by tapping the cables together,,,, has anyone else heard of a different reset procedure?

[gmtech4]

a scanner

[SantaFe]

I had a complete failure of the instrument cluster over time (no speed, no anything). Did a Google search on "cluster failure" and found a bunch of companies repairing them. Chose a guy in Texas, pulled the cluster (easy) and sent it. $135 later, got it back, installed, and it works fine. He replaced all steppers, lamps, flashed the program with an update and all is good. Note that the dealer was no help at all.

[2010.6.2L]

I had to replace the 4x4 selector switch on an 01 with the same problem.