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Service 4wd

ronnieb

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ronnieb Enthusiast

ronnieb

Posted
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This morning the truck showed a service 4wd error and the led on the 4wd switch was out. Didn't try to take it out of 2wd in case there was a problem. Well went out later today and drove the truck and no error this time, led on 4x4 switch working and shifted into 4x4 ok.

 

I borrowed an Actron cp9180 scanner, and it didn't pull any codes. I'm fairly sure this model will pull the C chassis codes because it's a higher end model. I'm somewhat hoping the problem will reappear so I can troubleshoot and fix. Anyone had intermitent 4wd service issues?

satori Enthusiast

satori

Posted
Posted

I've read on here that several issues can cause this. The most common problem seems to be the push-button switch in the dash.

 

However, in the case of my 2005 Tahoe, the problem was the sensor in the encoder motor assembly on the transfer case. It started out similar to what you're describing. Sometimes I would come out in the morning and the LED would say the transfer case was in neutral or 4-Lo, or it wouldn't be lit at all. I let it go for a long time because I could still get it back in to 2-Hi, but eventually it kept shifting itself into neutral while I was driving. The sensor was ~$70 and it took about an hour to change.

ronnieb Enthusiast

ronnieb

Posted
  • Author
Posted
I've read on here that several issues can cause this. The most common problem seems to be the push-button switch in the dash.

 

However, in the case of my 2005 Tahoe, the problem was the sensor in the encoder motor assembly on the transfer case. It started out similar to what you're describing. Sometimes I would come out in the morning and the LED would say the transfer case was in neutral or 4-Lo, or it wouldn't be lit at all. I let it go for a long time because I could still get it back in to 2-Hi, but eventually it kept shifting itself into neutral while I was driving. The sensor was ~$70 and it took about an hour to change.

 

I searched before posting and read about the switch failures and other causes, the problem is that the code went away. I was just checking to see if anyone else had experienced intermitent errors, and if there was a way to log the error. I just got through scanning again, and it passed without codes.

satori Enthusiast

satori

Posted
Posted

FWIW, mine didn't show any codes with my hand-held OBD-II scanner either. OnStar could only tell me that there was a problem with my 4WD system. A better scanner probably would have picked something up. I was "lucky" because the warranty history from before I bought the truck showed that this particular sensor had failed four times before, so I took a wild guess at the problem.

ronnieb Enthusiast

ronnieb

Posted
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FWIW, mine didn't show any codes with my hand-held OBD-II scanner either. OnStar could only tell me that there was a problem with my 4WD system. A better scanner probably would have picked something up. I was "lucky" because the warranty history from before I bought the truck showed that this particular sensor had failed four times before, so I took a wild guess at the problem.

 

The scanner I borrowed is an Actron cp9180, which should pickup the Chassis codes. It lists the Chassis codes in it's table for what its worth.

 

Drove the truck this morning and problem still hasn't come back...

Nick The Great Senior Enthusiast

Nick The Great

Posted
Posted

My light has come on 3 or 4 times in the year I've owned the truck. It always goes away on the next start up. Of course the truck has no way of telling you if the 4WD is activated anyway, so maybe it doesn't matter . . .

 

I'd like to get all of GM's Electrical Engineers in a room and punch each one in the face. :)

Matt_ Senior Enthusiast

Matt_

Posted
Posted

The code is stored, it doesn't go away. Your Actron can't read transmission trouble codes.

 

For 2003 the 2 most common causes are the switch and a programming glitch. There is a tsb for the programming.

rjgogo Enthusiast

rjgogo

Posted
Posted

I had the same thing happen on one of the colder days this winter. No error codes, I did a search here and found a post discussing a communications failure that is corrected by pulling a fuse under the hood. Pulled the fuse as directed for 30 seconds and was back in business. I don't remember the exact fuse but do a search, It also referenced a TSB. Mine was not the switch, I pulled that and it looked fine.

Matt_ Senior Enthusiast

Matt_

Posted
Posted

That's a good point... I don't know if the programming glitch leaves a code, I guess it makes sense that it wouldn't.

 

4wd Codes caused by hardware failures do not go away though, just to clarify that.

 

The fuse method often works, and is definitly worth a try- the price is right!

ronnieb Enthusiast

ronnieb

Posted
  • Author
Posted
The code is stored, it doesn't go away. Your Actron can't read transmission trouble codes.

 

For 2003 the 2 most common causes are the switch and a programming glitch. There is a tsb for the programming.

 

Yeah, just called up Actron and they loaded the code reference in the scanner, but it can't read the codes from the cpu. So looks like I may be making a trip to the dealer for a code scan.

 

I did an initial search for the tsb with no luck, you don't have any more info on the programming tsb handy do you?

Matt_ Senior Enthusiast

Matt_

Posted
Posted

I'll see if I can find it when I get home from work tonight. If you don't find it, and I don't post later, send me a PM to remind me.

Matt_ Senior Enthusiast

Matt_

Posted
Posted

Also you don't have to go to the dealer. Most good scanners ($$$$) can read it, call around - I'm sure some local shops can pull the code for you

 

I use a Snap-On Modus... Which isn't exactly the newest scanner on the market anymore

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