Transfer case control module on GMC Envoy

Average mileage: 133,000 (72,000–193,000)
Drive Train affected: 4WD
2 model years affected: 2002, 2004
5 people reported this problem
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problem details
2004 GMC Envoy 120,000 mi,
my envoy goes into 4 wheel drive without you putting it into 4 wheel drive
2002 GMC Envoy - 4WD 110,000 mi,
Battery went dead in the Envoy one day. After replacing the battery the 4 wheel drive indicator light would not change with the selector and the 4 wheel drive light came on. After researching online I found that the engineers at GM forgot to set up the transfer control module with anything to save the memory, so basicly, it didn't know what to do. It also said you could take it to a dealer and they could reflash it for $100 and hope you never have battery problems again or locate a used one (2003 or newer because GM corrected their screw up after 2002 models). Make sure you research and get one that matches your 2002. Mine came from Ebay for $35 and was from a 2003 Trailblazer and it works great and I don't have to worry about the memory being gone if the battery goes.
2002 GMC Envoy - 4WD 193,000 mi,
Battery would hold charge. When it was swapped for another battery, the 4wd light came on and the indicator lights no longer illuminated. Went to the dealership to reprogram the module. After waiting 2.5 hrs, they said my car was ready. After paying, the light came on as soon as I got into my car. Told them and they tried to flash it again, but no luck. Now, they are saying I need a new transfer case control module. ~$400+tax. IDK how difficult it is to fix, but I may have to try.
2002 GMC Envoy - 4WD 170,000 mi,
Will not go into 4wheel drive
2002 GMC Envoy - 4WD 72,000 mi,
Tccm fail not fixed yet