2002 GMC C1500 Transmission won't shift-panel guages failed

Some customers may comment on one or more of the following conditions:

"Â The Malfunction Indicator Lamp (MIL) is ON.

"Â The transmission is defaulted to second gear (4L80/85-E).

"Â The transmission is defaulted to third gear (4L60/65-E).

"Â The instrument cluster is inoperative.

Upon investigation, one or all of the diagnostic trouble codes (DTCs) P0740, P0753, P0758, P0785, P0787, P0973, P0976, P1860, P2761, P2764 and P2769 may be set depending on the vehicle.

Cause
The most likely cause of this condition may be a loss of voltage to the transmission solenoid power supply circuit.

This condition may also be the result of an incorrect installation of an aftermarket electronic device such as a remote starter or alarm system. With the ignition switch in the RUN position, test for battery voltage at the circuit fuse in the transmission solenoid power supply circuit, If battery voltage is present at the fuse, inspect the ignition voltage circuit between the fuse and the transmission for possible opens.
If battery voltage is not present at the fuse, test for continuity between the fuse and the ignition switch. If NO continuity is between the fuse and the ignition switch, repair the open in that circuit.
If you have continuity between the fuse and the ignition switch, the most likely cause is the ignition switch. Replace the ignition switch. Follow this info and post back with what you find.