P0731-GEAR RATIO ERROR IN 1STFor a complete wiring diagram Refer to Section 8W.Theory of OperationThe transmission system uses two speed sensors, one to measure input rpm and one to measure output rpm. These inputs are essential for proper transmission operation. Therefore, the integrity
of this data is verified through data checks. When in gear, if the gear ratio does not compare to a known gear ratio, the corresponding gear ratio error trouble code is set. The transmission will go into
limp-in mode after four gear ratio error events occur in a given driving cycle.- When Monitored:The Transmission gear ratio is monitored continuously while the transmission is in gear.
- Set Condition:If the ratio of the Input rpm to the Output rpm does not match the current gear ratio when compared to the known gear ratio.
Possible Causes
RELATED TRANSMISSION DTCS PRESENT
INTERMITTENT GEAR RATIO ERRORS
INTERNAL TRANSMISSION
Always perform the 42RLE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC
- 42RLE - STANDARD PROCEDURE) Diagnostic Test1. DETERMINING IF RELATED TRANSMISSION DTCS ARE PRESENTWith the scan tool, read Transmission DTCs.If any of these DTCs are present, perform their respective tests first.Are there any Loss of Prime, Line Pressure Sensor and/or Speed Sensor DTCs present?Yes- Refer to appropriate diagnostic procedure in the Transmission category. If any of these DTC's are present, they will cause a gear ratio error. Perform the
test for Loss of Prime first if it is present.
No- Go To 2
2. CHECK TO SEE IF P0731 IS CURRENTWith the scan tool, perform the 1st gear clutch test. Follow the instructions on the scan tool.Increase the throttle angle or TPS Degree to 30° for no more than a few seconds.Do not overheat the transmission.Did the Clutch Test pass, Input Speed remain at zero?Yes- Go To 3
No- Repair internal Transmission as necessary. Check all of the components related to the UD and LR clutches. Inspect the Oil Pump and repair or replace as necessary.
Refer to the Service Information for the proper repair procedures.
- Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)
3. CHECK FOR INTERMITTENT OPERATIONThe conditions to set this DTC are not current at this time.Check the gearshift linkage adjustment.Gear ratio DTCs can be set by problems in the Input and Output Speed Sensor circuits. If the vehicle passes the Clutch Test and still sets Gear Ratio DTC, check the Speed Sensors for proper
operation.Remove the Ignition Switch Feed fuse from the TIPM.Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear. The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in personal injury or death.Install the Transmission Simulator, Miller tool #8333 and the Electronic Transmission Adapter kit.Check the wiring and connectors for the Speed Sensors for a good connection, then perform a wiggle test using the Transmission Simulator.This DTC can also be set under extreme temperature conditions. This is usually caused by an internal problem. Verify if the problem is only experienced under extreme hot or cold conditions.With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.Check for Service Information Tune-ups or Service Bulletins for any possible causes that may apply.Were there any problems found?Yes- Repair as necessary.
- Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)
No- Test Complete.