P0731

ALLISON AUTOMATIC TRANSMISSION

DTC P0731





Circuit Description for Allison Automatic Transmission
The Transmission Control Module (TCM) uses input from the turbine speed sensor and the output speed sensor to determine gear ratios. The TCM then compares the known gear ratio to the calculated gear ratio for the current range.
DTC P0731 is a type A DTC.

Conditions for Running the DTC
^ The components are powered and ignition voltage is greater than 9 V and less than 18 V.
^ Output speed exceeds 200 RPM.
^ First range is selected and attained.
^ DTCs P0716, P0717, P0721, P0722, P0726, and P0727 are not active.

Conditions for Setting the DTC
DTC P0731 sets when the calculated first range ratio, steady state, differs from the known first range ratio.

Action Taken When the DTC Sets
^ Fails to 2nd or 5th range while diagnostic response is active.
^ If the shift selector is moved to NEUTRAL, then the transmission will shift to NEUTRAL.
^ If the shift selector is moved to REVERSE, then the transmission will either lock in NEUTRAL or shift to REVERSE, unless the transmission is compromised by overspending or direction change, then the transmission will lock in NEUTRAL.
^ DTC P0731 will be stored in the TCM history.
^ Illuminate MIL when active.
^ The TCM freezes shift adapts (DNA).
^ TCM inhibits TCC engagement.

Conditions for Clearing the MIL/DTC
A scan tool can clear the code from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
^ Incorrect TCM calibration will cause this DTC to set.
^ Incorrect ratio codes typically indicate mechanical conditions with specific clutches, i.e. C1 or C5 for first range.
^ Incorrect ratio code could indicate hydraulically failed solenoid. Check DTC information for specific solenoid.
^ You may have to drive the vehicle to experience fault. Clutch test mode can be used to check stall speed.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step tests ignition voltage.
4. This step tests for current first range ratio.
5. This step tests speed sensor readings.
6. This step tests for clutch slippage in first range shown by turbine speed not remaining at zero.
7. This step checks for evidence of clutch failure.