DTC 21 - P1781

Name of Code:
P-1781(21) - 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 condition will only occur if code P-1781(21) is present with a code P-0705(28).

Possible Causes:
- If code P-1791(35) is present, ignore code P-1781(21) and perform code P-1791 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
- TCM