$21 (P1781) - OD Pressure Switch Sense Circuit

Name of code: $21 (P1781) - OD Pressure Switch Sense Circuit

When monitored: Whenever the engine is running.

Set condition: This code is set if the OD pressure switch is open or closed at the wrong time in a given gear (see chart below).

Theory of operation: The Transmission system uses three pressure switches to monitor the fluid pressure in the L-R, 2-4, and OD clutch circuits. The pressure switches are continuously monitored for the correct states in each gear as shown below.





Transmission Effects: Normal operation will be experienced if no other fault codes are present. TCM will ignore the code. Limp-in and MIL illumination will only occur if code 21 (P1781) is present with a code 28(PO705).

Possible causes:
- If code 35(P1 791) is present, ignore code 21 (P1 781) and perform code 35(P1 791) diagnostic procedures
- OD pressure switch sense circuit open or shorted to ground between TCM and solenoid pack
- OD pressure switch sense circuit shorted to battery
- Solenoid pack defective
- Loose valve body bolts
- Plugged filter - internal transmission or torque converter failure
- Defective TCM