Powertrain Controls - ECM/PCM

Transmission Range (TR) Pressure Switch Assembly Circuit Check:

Transmission Range (TR) Pressure Switch Assembly Circuit:

CIRCUIT DESCRIPTION
The Transmission Range (TR) switch assembly consists of five normally open pressure switches mounted on the valve body. The Transmission Control Module (TCM) supplies battery voltage to each range signal. By grounding one or more of these circuits through various combinations of the pressure switches, the TCM 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 TCM will be removed, D2 will be indicated.

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

ACTION TAKEN (TCM will default to)
^ Drive four shift pattern control.
^ No fourth gear in hot mode.
^ No Torque Converter Clutch (TCC).

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 chart.
1. This test checks the indicated range signal to the manual valve position actually selected.
2. This test checks for correct voltage from the TCM to the transmission external connector
3. This test checks for a short to ground from the TCM to the transmission external connector in any one of the three circuits.

DIAGNOSTIC AIDS
DTC 28 will set if the TCM 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.
Refer to "TR Pressure Switch Assembly Resistance Check" or "Functional Test Procedure" for further information. Testing and Inspection