Test Procedure

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

If a No Forward, No REVERSE, or Will Not Move condition occurs:

Set the parking brake.
With the ignition OFF, disconnect the 80-way connector at the transmission control module (TCM).
Using a fused jumper wire, connect terminal R of the automatic transmission inline 20-way connector to a known good ground.
Start the engine and move the range selector to REVERSE position.
The transmission should engage REVERSE range.
Move the range selector to the D position.
The transmission should engage THIRD range.

If REVERSE and THIRD range are available in Limp Home Mode, an electrical failure may be indicated. If only 1 of the 2 ranges, or neither, was obtainable, this may indicate an internal hydraulic failure such as one of the following:

Failed clutch
Stuck valve
Solenoid failure

The clutches that could possibly have an indicated failure in Limp Home are the 1-2-3-4 clutch, the 3rd, 5th and reverse clutch, and the low and reverse clutch.