2003 GMC 4WD Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SMORT · 01-25-2010, 06:40 PM

I just replaced the transfer case due to the pump rub problem. Got everything in and running fine for couple of weeks now. This morning the check 4wd light is on and none of the indicator lites (2hi,4hi,4lo,auto4wd)are on. Drives fine though Any ideas??

Benelli · 01-25-2010, 07:05 PM

Have you scanned it? I'd start there.

DirtyLarry · 01-25-2010, 11:56 PM

Chances are the previous issue and the latest service 4wd is not related. GM’s electric shift 4wd system is pretty famous for dropping Service 4wd lights. The system is just too complicated to do the job of what a simple lever used to do before people that should be driving cars started driving trucks resulting in all the manufactures making electric shift the norm instead of the exception. This isn’t just a GM issue…. Dodge, Ford, Toyota and the rest have the same issues.

In GM’s case, chances are the control head failed (button assembly on the dash) but transfercase control module failures (TCCM) and encoder motor (motor on side of tcase that is constantly gets soaked with dirt and road salt) or any of the 12 lbs of wiring that support the system has chaffed on something due to GM's piss poor wiring harness routing are all very common failure modes as well.

As Benelli stated, pull the codes and see where that leads you. You will probably find the control head switch died, which is the cheapest part…luckily. The TCCM is the pricy piece and more common to fail on TrailBlazer’s and Envoy’s but GMT800 trucks are not excluded.

I have 3 GMT800 rigs. 2 of which have levers on the floor for these reasons. I had to settle with the electric shift crap on the 3rd because it was standard on SUVs after 2000 model year.

SMORT · 01-30-2010, 05:52 PM

Thanks for the replys, seems to be the dash swich.

01-25-2010, 06:40 PM	#1
SMORT Registered User Join Date: Jan 2010 Location: Timberlake,NC Posts: 12	2003 GMC 4WD Question I just replaced the transfer case due to the pump rub problem. Got everything in and running fine for couple of weeks now. This morning the check 4wd light is on and none of the indicator lites (2hi,4hi,4lo,auto4wd)are on. Drives fine though Any ideas?? Last edited by SMORT; 01-25-2010 at 06:41 PM.

01-25-2010, 07:05 PM	#2
Benelli Watchin the rust grow Join Date: Oct 2008 Location: Western Nebraska Posts: 950	Re: 2003 GMC 4WD Question Have you scanned it? I'd start there. __________________ 1979 Chevy K10 (H/D Front end) - 350 w/ Holley Truck Avenger, Weinald Intake manifold, headers, bored .060 over, mild cam, Built up TH350 (TranStar Shift kit) with a part-timed NP203 t-case SOLD ($3,000) 1997 Chevy Silverado 1500 - 4.3 vortec, extended cab, 21 highway MPG, stock. "Red" SOLD ($3,000) 1987 Toyota 4wd Pick-up - work in progress, future DD SOLD ($1,850) 1998 Dodge Ram 2500 Cummins 5spd Quad cab - old 12 valve with some work done 2004 Chevy Silverado - Black, 4x4, 5.3L, stock for now Underneath that rust is a heart of gold

01-25-2010, 11:56 PM	#3
DirtyLarry Windy Corner of a Dirty Street Join Date: Jun 2003 Location: Pueblo West, Colorado Posts: 2,926	Re: 2003 GMC 4WD Question Chances are the previous issue and the latest service 4wd is not related. GM’s electric shift 4wd system is pretty famous for dropping Service 4wd lights. The system is just too complicated to do the job of what a simple lever used to do before people that should be driving cars started driving trucks resulting in all the manufactures making electric shift the norm instead of the exception. This isn’t just a GM issue…. Dodge, Ford, Toyota and the rest have the same issues. In GM’s case, chances are the control head failed (button assembly on the dash) but transfercase control module failures (TCCM) and encoder motor (motor on side of tcase that is constantly gets soaked with dirt and road salt) or any of the 12 lbs of wiring that support the system has chaffed on something due to GM's piss poor wiring harness routing are all very common failure modes as well. As Benelli stated, pull the codes and see where that leads you. You will probably find the control head switch died, which is the cheapest part…luckily. The TCCM is the pricy piece and more common to fail on TrailBlazer’s and Envoy’s but GMT800 trucks are not excluded. I have 3 GMT800 rigs. 2 of which have levers on the floor for these reasons. I had to settle with the electric shift crap on the 3rd because it was standard on SUVs after 2000 model year. __________________ Current vehicle collection: 1978 Chevrolet K10, 8.1L, NV4500, NP205 1989 Chevrolet Suburban, 8.1L, NV4500, NP241 1993 Chevrolet C1500 Sportside, TBI 7.4L, 4L60E 2001 Chevrolet K2500HD, Ext Cab, SWB, 8.1L, ZF 6 speed 2014 Chevrolet Impala LTZ 3.6L Vortec 8.1L because life is too short to tolerate underpowered vehicles Instagram

01-30-2010, 05:52 PM	#4
SMORT Registered User Join Date: Jan 2010 Location: Timberlake,NC Posts: 12	Re: 2003 GMC 4WD Question Thanks for the replys, seems to be the dash swich.



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