GM Service Manual Online
For 1990-2009 cars only

Condition

Action

DEFINITION: No 2-1 downshift

Park/neutral position switch (72)

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

Transmission control module (TCM)

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

Valve body (39)

Replace the valve body (39).

Internal transmission part failure

    â€¢ 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
    â€¢ Replace transmission if any internal parts are faulty.