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Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 27878
Experience:  14 years GM dealer Technician.
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2000 Chevy Silverado 1500 4WD will not work Symptoms: No 4WD

Customer Question

2000 Chevy Silverado 1500 4WD will not work
No 4WD service light
No lights in switch assembly even at key on
Buttons have no affect on 4WD system (truck stuck in 2H)
Steps taken:
1. Cleaned the grounding point below the drivers door
2. Replaced 4WD switch assembly
3. Replaced TCCM
4. Tried to reset the TCCM with the following procedure {disconnected battery for 30 min, reconnected battery, started truck, pulled ATCM fuse, waited 30 sec, reinstalled ATCM fuse, restarted truck}
None of the repair/replacements had any change on system behavior, any expertise you can offer would be greatly appreciated.
Submitted: 1 year ago.
Category: Chevy
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Was the TCCM programmed after it was installed or did it come pre programmed ready to install?

Have you tried to disconnect the transfer case actuator to see if the lights then come back on?

Let me know so we can continue,thanks Pete.

Customer: replied 1 year ago.
The TCCM is a Dorman is is supposed to be pre-programmed and ready to use.
We did not try disconnecting the actuator and validating the lightsI added two files that show the power and ground wires we checked in the system. as shown on the selector switch diagram we were unable to get the 8V signal from the TCCM to the switch. however the wire checked good for continuity between the two components.
Expert:  Pete replied 1 year ago.

O.k.,check this 8 volt wire for a short or resistance to ground or power with the switch and the TCCM unplugged.If there is resistance to ground or resistance to voltage this indicates this wire is shorted and needs traced to locate and repair the source of the short.

If this wire checks out o.k. unplug the encoder motor at the transfer case,pull the 4wd fuse for about 5 minutes then reinstall it and see if it lights up then or if you then get a service 4wd fault.I have seen the encoder motor short out and damage the TCCM or cause the TCCM to act up.Let me know if you come up with anything here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 1 year ago.
Wire checks good and unplugging the encoder, pulling the fuse, reinstalling the fuse did not generate any lights
Expert:  Pete replied 1 year ago.

The only thing I can think of here is that the TCCM that was installed either does need programmed or is programming incorrectly for your model here or was faulty out of the package needing replaced again.If you can I would see if the facility you receives the TCCM from will parts warranty it for you at no cost to you and see if this resolves the issue here.With the correct power and grounds at the TCCM and no wiring faults the switch should light up.

Thanks Pete