TFP Manual Valve Position Switch Circuit Diagnosis

Circuit Description - 4T80-E Automatic Transaxle
The automatic Transmission Fluid Pressure (TFP) manual valve position switch consists of two normally-open pressure switches. The assembly is attached to the lower control valve body.
The PCM supplies ignition voltage on the two range signal circuits, signal circuit A and signal circuit C. By grounding one of the switches with fluid pressure from the manual valve, the PCM detects a garage shift of PARK/NEUTRAL to REVERSE or DRIVE (D1, D2, D3, or D4). Refer to the Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic. table. This information is used by the PCM in order to adjust line pressure during garage shifts.
If one of the following conditions occur, garage shifts may become harsh:
^ An open signal circuit
^ A signal circuit shorted to ground
^ A damaged or leaking pressure switch seal
^ Sediment or debris in a pressure switch
^ Damaged or stuck pressure switch contacts

Diagnostic Aids
^ Inspect the connections at the PCM, the TFP manual valve position switch and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Diagrams/Diagnostic Aids.
^ Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical/Intermittents in Diagrams/Diagnostic Aids.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests the indicated range signal to the manual valve range actually selected.
4. This step tests for correct voltage from the PCM.