GM Service Manual Online
For 1990-2009 cars only

Condition

Action

DEFINITION: No 1-2 upshift

Park/neutral position switch (72)

    • Perform functional test on the park/neutral position switch (72).
    • Replace park/neutral position switch (72) if fails test.

Transmission control module (TCM)

    • Inspect for operation of TCM and correct calibration.
    • Re-cal TCM if necessary.
    • Replace the TCM if faulty.

Valve body (39)

Replace the valve body (39).

Internal transmission part failure

    • Disassemble the transmission and inspect the following:
       - Clutch assembly, O-rings cut or damaged, clutch disc failure
       - Fluid pump worn or scored components
       - Broken shafts or gears
    • Replace transmission if any internal parts are faulty.