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.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0731 Incorrect 1st Gear Ratio

Conditions for Running the DTC
^ DTCs P0716, P0717, P0721, P0722, P0726, P0727, P0875, and P0876 are not active.
^ The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
^ Output speed exceeds 200 RPM.
^ First range is selected and attained.

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
^ The TCM illuminates the malfunction indicator lamp (MIL).
^ The transmission defaults to 2nd or 5th range while diagnostic response is active.
^ If the shift selector is moved to NEUTRAL, the transmission will shift to NEUTRAL.
^ If the shift selector is moved to REVERSE, the transmission will either lock in NEUTRAL or shift to REVERSE, unless the transmission is compromised by over speeding or direction change. If this occurs, the transmission will lock in NEUTRAL.
^ DTC P0731 will be stored in TCM history.
^ The TCM freezes shift adapts.
^ The TCM inhibits torque converter clutch (TCC) engagement.

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

Diagnostic Aids
^ Incorrect ratio codes typically indicate mechanical conditions with specific clutches, such as C1 or C5 for first range.
^ Incorrect ratio code could indicate a hydraulically failed solenoid. Observe DTC information for the specific solenoid.
^ Clutch test mode can be used to measure stall speed.
^ You may have to drive the vehicle in order to experience a condition.

Test Description








The numbers below refer to the step numbers on the diagnostic table.
3. This step tests ignition voltage.
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.