GM Service Manual Online
For 1990-2009 cars only

Third Gear Only

Checks

Cause

PCM and Transmission Wiring

    â€¢ Loose connector
    â€¢ Corroded connector
    â€¢ Defective PCM

Generator and Wiring

    â€¢ Loose connector
    â€¢ Corroded connector
    â€¢ Defective generator

Speed Sensor and Wiring

    â€¢ Loose connector
    â€¢ Corroded connector
    â€¢ Defective speed sensor

PCM and Wiring 1-2 and 2-3 Shift Solenoid Valves

    â€¢ Loose connector
    â€¢ Corroded connector
    â€¢ Defective quad driver