Powertrain Controls - ECM/PCM

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION
The Transmission Range (TR) switch assembly consists of five normally open pressure switches mounted on the valve body. The PCM supplies battery voltage to each range signal. By grounding one or more of these circuits through various combinations of the pressure switches, the PCM detects what transmission range has been selected by the vehicle operator. When the transmission electrical connector is disconnected, the ground potential for the three range signals to the PCM will be removed, and D2 will be indicated.

DTC 28 WILL SET WHEN
^ Range signals "A" and "C," are both zero volts.
^ All conditions met for 2 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
^ No Torque Converter Clutch (TCC).
^ Drive 4 shift control.
^ Disable manual mode.
^ No fourth gear in hot mode.

DTC 28 WILL CLEAR WHEN
The fault condition(s) no longer exist, and the ignition switch is cycled from "OFF" then "ON."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic charts.
1. This test checks the indicated range signal to the manual valve position actually selected.
2. This test checks for correct voltage from the PCM to the transmission external connector.
3. This test checks a short to ground or an open in any one of the three circuits.

DIAGNOSTIC AIDS
DTC 28 will set if the PCM detects one of two "Illegal" combinations.

Refer to accompanying chart for various A/B/C range combinations.

Check all wiring connectors for proper terminal tension.