# Servie 4WD 03 2500HD



## ChevKid03 (Dec 23, 2007)

I had the Service 4WD light come on today after starting the truck. The truck just hit 100k yesterday. No noises, no problems to cause this. Anyone have any ideas?


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## B&B (Nov 4, 2006)

Could be a ton of things... need to have it scanned for body codes to try and narrow it down. 

Generic parts store scanner wont do it, need a good professional scanner or Tech2 to pull body codes.


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## ChevKid03 (Dec 23, 2007)

Thanks. I'm going to go fire it up today and see what happens. It came up one other time at around 60k and never came back. I was using 4wd on and off for a while yesterday just when I was doing some driveways since the snot was heavy and wet. At least it broke after the last one was clean. Will it still have codes if the check engine light doesn't come on?


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## mike33087 (Feb 9, 2005)

that happened to my truck twice... when it did it all the lights on the 4x4 buttons turned off and wouldnt let you select any 4x4 mood.... i checked the fuse and it was fine. when i put it back in everything was back to normal.... and every thing to do with the 4x4 worked.


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## lehmand1 (Dec 17, 2007)

I would also like to know what caused this. It happened to me last month on my 03 1500 and I was in 2wd plowing. When it came on it wouldnt let me select any 4wd functions. I just shut the truck off, restarted it, and everything was fine and still works.


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## RBRONKEMA GHTFD (Dec 17, 2006)

I had this 2 months ago on my 04 sierra, it ended up being that the plug was dirty and wasn't making contact with the prongs. I am looking at the paper work that my dealer game me after they had it on the tester and I don't know where to start. I am looking to tell you what code it was for me and it says 161 electrical minor, Then it says 31883 check over and has U 1003,U1009 DOC 1740222 They are false
Codes set by a garbled class 2 message clean grounds 100,104, 108, 110 cleared codes reporgramed tccm per doc 1848894 for selector swtich not working and service 4X4 ligth on lop K4121 I don't know what this means but maybe it'll help

Ryan


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## Sno4U (Dec 30, 2003)

Sometimes codes like that are set to go off at standard maintenance intervals.
Our Jeep had check engine light come on at some really weird mileage on a long trip, so, I stopped, checked oil, tranny and motor. All the guages where reading Ok so I kept on going. So when we got her home the mechanic scanned it and it didn't mean anything was "really" wrong it just was supposed to have the O2 sensor or something stupid like that changed


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## RBRONKEMA GHTFD (Dec 17, 2006)

Well when mine came on my 4X4 didn't work at all. I tried putting it on ice just to see, and nope not a thing, Non of the 4X4, 4low and 2wd lights were on either so i knew somthing was worng.


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## B&B (Nov 4, 2006)

ChevKid03;525823 said:


> It came up one other time at around 60k and never came back. I was using 4wd on and off for a while yesterday just when I was doing some driveways since the snot was heavy and wet. At least it broke after the last one was clean. Will it still have codes if the check engine light doesn't come on?


 Did the 4WD still work after the service light came on?

Yes, if it set a code it will store the code for 30-50 key on/off run cycles.

If you want to give it a quick check you can check the connector plug on the encoder motor and especially the ground wires for the 4WD system. They teminate at a bolt on the outboard side of the dr side frame rail right under the dr door. They have been known to cause troubles just like this.

Like I mentioned CK, scanning it is the quickest way to pinpoint a problem such as this. Don't throw parts at it as they're not cheap. Keep us updated on what you find.


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## B&B (Nov 4, 2006)

Sno4U;526870 said:


> Sometimes codes like that are set to go off at standard maintenance intervals.
> Our Jeep had check engine light come on at some really weird mileage on a long trip, so, I stopped, checked oil, tranny and motor. All the guages where reading Ok so I kept on going. So when we got her home the mechanic scanned it and it didn't mean anything was "really" wrong


The Chrysler's are famous for that and have been that way for years. It's for "emissions maintenance"..and usually at around 60,000 mi.

But not on a GM truck...


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## B&B (Nov 4, 2006)

RBRONKEMA GHTFD;526865 said:


> I am looking at the paper work that my dealer game me after they had it on the tester and I don't know where to start. I am looking to tell you what code it was for me and it says 161 electrical minor, Then it says 31883 check over and has U 1003,U1009 DOC 1740222 They are false
> Codes set by a garbled class 2 message clean grounds 100,104, 108, 110 cleared codes reporgramed tccm per doc 1848894 for selector swtich not working and service 4X4 ligth on lop K4121 I don't know what this means but maybe it'll help
> 
> Ryan


Judging by your description it sounds like yours is the push button 4WD system. The manual floor shift equipped trucks don't use any class 2 data serial connection for the 4WD system. Only the push button trucks do.

I see that they cleaned the grounds... like I said in my post to Chevykid, those grounds have been known to cause problems like this.

The #'s 100, 104,108 and 110 are the ground wire designations in the wiring diagram..helps trace each wire and tell's the tech the origin and termination of the specific wire through the wiring harness.

Grounds 100,104, 108, and 110 all terminate at the bolt on the dr side frame rail that I mentioned before.


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## ticki2 (Jan 10, 2006)

Here is my service 4WD saga. First time while in 2WD all the lights on the switch started flashing and could not change function. Truck ran fine in 2WD. Shut off truck and restart and back to normal. A few months later service 4WD comes on and only the neutral light on the switch is on , hit a function on the steering wheel and everything is good. This went on periodically for about a year . Cleaned all the grounds and no change. Finally decided to replace the switch and all has been good for 6 months. One other observation , when the neutral light on the switch was on cruise control would not engage and there was no service 4 WD light on.

Your results may vary, good luck.


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## Sno4U (Dec 30, 2003)

B&B;527032 said:


> The Chrysler's are famous for that and have been that way for years. It's for "emissions maintenance"..and usually at around 60,000 mi.
> 
> But not on a GM truck...


B&B You know your stuff!!!
Ya it was some really weird mileage, like 63,588 or something like that. But yes your exactly rite!


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## B&B (Nov 4, 2006)

Sno4U;527953 said:


> B&B You know your stuff!!!


Well..I did stay at a Holiday Inn express last night .


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## BigLou80 (Feb 25, 2008)

RBRONKEMA GHTFD;526865 said:


> I had this 2 months ago on my 04 sierra, it ended up being that the plug was dirty and wasn't making contact with the prongs. I am looking at the paper work that my dealer game me after they had it on the tester and I don't know where to start. I am looking to tell you what code it was for me and it says 161 electrical minor, Then it says 31883 check over and has U 1003,U1009 DOC 1740222 They are false
> Codes set by a garbled class 2 message clean grounds 100,104, 108, 110 cleared codes reporgramed tccm per doc 1848894 for selector swtich not working and service 4X4 ligth on lop K4121 I don't know what this means but maybe it'll help
> 
> Ryan


Thanks for all this information. My truck (02 GMC 2500hd) is stuck in 4wd, The selector will not let me change in to two wheel drive and the service 4wd light is on. I had a body scan done this afternoon and it was a U code, I guess there is a 8 volt reference signal that the tc cm generates that the main body computer is not reading. But maybe thats flase as you have stated. I will print this out and take it to the mechanic in the morning. Thanks so much
Lou

Lou


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## ChevKid03 (Dec 23, 2007)

B&B;527031 said:


> Did the 4WD still work after the service light came on?
> 
> Yes, if it set a code it will store the code for 30-50 key on/off run cycles.
> 
> ...


I'm wondering if it is set to come on at certain mileage intervals... I've used the truck quite a few times since the "Service 4WD" light came on and it has been fine ever since... If I get a chance to get it scanned in-between work I'll let you guys know. thanks!


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## B&B (Nov 4, 2006)

ChevKid03;528109 said:


> I'm wondering if it is set to come on at certain mileage intervals... I've used the truck quite a few times since the "Service 4WD" light came on and it has been fine ever since... If I get a chance to get it scanned in-between work I'll let you guys know. thanks!


GM doesn't use the "random service reminder light" deal to inform the owner of basic service on the 4WD systems on these full size trucks.


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## ChevKid03 (Dec 23, 2007)

B&B;528137 said:


> GM doesn't use the "random service reminder light" deal to inform the owner of basic service on the 4WD systems on these full size trucks.


good to know..... I'll dig deeper then... thanks B&B


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## B&B (Nov 4, 2006)

:salute: Keep us posted on your findings CK.


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