P0731

Diagnostic Chart:

The transaxle control module (TCM) uses the transaxle input speed sensor (ISS) and transaxle output speed sensor (OSS) to determine input shaft speed and output shaft speed. These sensor readings are used to determine the current gear ratio. The TCM uses this information to determine if the commanded gear matches the actual gear. DTC P0731 sets if 1st gear is commanded and The TCM detects an actual gear ratio other than 1st gear.

DTC PARAMETERS
DTC P0731 sets if 1st gear is commanded and the TCM detects an actual gear ratio other than 1st gear when:
^ Ignition voltage is at least 10.5 volts
^ Engine Speed is at least 400 RPM
^ Transaxle has been in a forward gear for at least 8 seconds
^ APP Angle is at least 40%
^ Transmission OSS is between 500 RPM and 1260 RPM.
^ Condition exists for 5 seconds

DTC P0731 diagnostic runs continuously when the above conditions have been met.

The TCM will command Trans. protection mode On if this DTC is active.

DTC P0731 is a type A DTC.

DIAGNOSTIC AIDS

IMPORTANT: If DTC P0717, P0722, P0963, P0973, P0974, P0976, P0977, P0979, P0980, P0982, or P0983 is set, diagnose that DTC first.

Observe Transmission ISS and Transmission OSS with a Scan tool. Compare with a known good vehicle to determine if the speed sensors are reading correctly.

Shift solenoids 2 and 4 do not produce any audible click noises when turned on or off. Shift solenoids 2 and 4 may not be tested by listening for audible click noises. Use the symptom chart to determine if shift solenoids 2 or 4 may be stuck open or closed.

Shift solenoid 1 produces an audible click noise when turned ON, but may not when turned OFF. Do not replace shift solenoid 1 because it does not click OFF.

Possible causes of incorrect 1st gear ratio:
^ Shift solenoid 1 stuck open
^ Shift solenoid 2 stuck closed
^ Shift solenoid 3 stuck closed
^ Shift solenoid 4 stuck closed
^ Line pressure control solenoid stuck closed
^ Valvebody
^ Forward Clutch (C1)
^ 12, reverse Clutch (B5)
^ Front internal gear sprag (F2)
^ Inaccurate speed sensors
^ TCM

1st gear ratio: 4.602:1 without engine braking.