Transmission Will Not Shift to Forward or Reverse

WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Condition	Action
Engine RPM too high	Reduce the engine RPM. It may be necessary to select NEUTRAL, and then D or R again.
Low fluid level	Add fluid to the proper level. Refer to Transmission Fluid Check .
Faulty throttle signal from engine	Correct the engine throttle signal.
Shift selector is not functioning properly	Repair the shift selector.
Speed sensor or sensors not functioning properly	Repair or replace the speed sensor or sensors or circuitry. Refer to Speed Sensor Replacement .
Mechanical failure to Low and Reverse clutch	Repair the transmission.
Mechanical failure in transmission torque converter, shafts, or planetaries	Repair the transmission.
Low pressure	Repair the transmission.
Faulty wiring in transmission control module (TCM) input/output function circuits	Correct the circuit wiring.