Test Description

WARNING: This page is about a different car, the 1995 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Test numbers refer to numbers on diagnostic chart.

Checks indicated range signal to valve position signal actually selected.
Checks for correct voltage from PCM to transmission external connector.
Checks for short to ground in any one of the 3 valve position circuits.

Fig 1: Code 28 Schematic (Corvette) Transmission Range Pressure Switch

Fig 2: Code 28 Diagnostic Flow Chart (Corvette) Transmission Range Pressure Switch