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Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 17169
Experience:  GCM master tech over 25 years
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2002 gmc envoy with c0550 code, service 4x4x light on,

Customer Question

2002 gmc envoy with c0550 code, service 4x4x light on, indicator lights on switch not illuminated, no 4x4 functions. replaced tcscm and now 550 is gone, light is off, still no 4x4 operation, no switch lights and a u1000 code present and in history. can communicate with tcscm but no functions available. how do I diagnose this code. I see you answered this question before and gave a 14 step diagnostic chart for this code. the actual steps are blank though. can you supply that flow chart for this
Submitted: 2 years ago.
Category: GMC
Expert:  Gary replied 2 years ago.

I am sorry for the long wait

when you installed the new TCCM was it installed and then programmed to the trucks VIN number with a programming scan tool with software ?

Expert:  Gary replied 2 years ago.

how are you making out ?