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  • P0731 Gear Ratio Error In 1st

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    When Monitored and Set Condition:

    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. This DTC can take up to five minutes of problem identification before illuminating the MIL.




    NOTE: Low fluid level can be the cause of many transmission problems. If the fluid level is low locate and repair the leak then check and adjust the fluid level. Refer to appropriate AUTOMATIC TRANSMISSION article.

    NOTE: Always perform diagnostics with a fully charged battery to avoid false symptoms.

    NOTE: Diagnose 1 Trip Failures as a fully matured DTC.

    NOTE: Verify flash level of Powertrain Controller. Some problems are corrected by software upgrades to the Transmission and Engine Systems.

    NOTE: Due to the integration of the Powertrain and Transmission control modules - if a controller flash is performed it is necessary to perform STANDARD PROCEDURE - TCM QUICK LEARN and the STANDARD PROCEDURE - DRIVE LEARN . Failure to do so may result in shift quality complaints.

    NOTE: Check for applicable TSB's that may apply.

    1. With the DRBIII(R), read the engine DTC's. Check and repair all Engine DTC's prior to performing Transmission symptom diagnostics. With the DRBIII(R), read Transmission DTC's. Record all DTC's and 1 Trip Failures. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors. Repair as necessary. Perform the Shift Lever Position Test. If the test does not pass, refer to Symptom test for SYMPTOM: P0706-CHECK SHIFTER SIGNAL . For Gear Ratio DTC's, check and record all CVI's. Most DTC's set on start up but some must be set by driving the vehicle to ensure that all diagnostic monitors have run. Perform this procedure prior to Symptom diagnosis. Continue Go To 2
    2. With the DRBIII(R), check for other transmission DTCs If any of these DTCs are present, perform their respective tests first. Are DTCs P0944, P0715, P0720, P1794, P0867, P0932, P0868, or P0869 present also?
      Yes --> Refer to the Transmission Category and perform the appropriate symptom. If any of these DTCs are present, they may cause a Speed Ratio Error. Perform the test for P0944 first if it is
      present. Perform (NGC) 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
      No --> Go To 3
    3. With the DRBIII(R), perform the 1st Gear Clutch Test. Follow the instructions on the DRBIII(R). Increase the throttle angle or TPS Degree to 30° for no more than a few seconds.
      CAUTION: Do not overheat the transmission. Did the Clutch Test pass, Input Speed remain at zero?
      Yes --> Go To 4
      No --> Go To 5
    4. The conditions to set this DTC are not currently present. With the DRBIII(R), check the EATX DTC EVENT DATA to help identify the conditions in which the DTC was set.
      If the DTC Event Data shows fault P0731 was set in the Park, Reverse, or Neutral, replace the Powertrain Control Module.
      If the DTC Event Data shows fault P0731 set with input RPM = zero, check input speed sensor and related wiring.
      If the DTC Event Data shows fault P0731 set with line pressure significantly below Desired Line Pressure, check for cause of low line pressure (i.e., oil level, misinstalled or damages filter or filter seal, sticking main regulator valve in pump, etc.).
      If the DTC Event Data shows fault P0731 set with UD pressure switch open (but line pressure matches Desired Line Pressure), air check the UD clutch passage for leakage and if OK, replace the solenoid assembly.Check the gearshift linkage adjustment.
      Intermittent Gear Ratio DTCs can be set by problems in the Input and Output Speed Sensor circuits and/or Speed Sensor Ground circuit. Remove the Starter Relay from the PDC.
      NOTE: Failure to remove the Starter Relay can cause a Transmission - No Response condition.
      Install Transmission Simulator, Miller tool # 8333.
      Wiggle wiring and connectors while checking for intermittent operation with the Transmission Simulator. Gear ratio DTCs 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. Were there any problems found.
      Yes --> Repair as necessary. Perform (NGC) 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
      No --> Test Complete.
    5. Repair internal transmission as necessary. Refer to the appropriate OVERHAUL article. If there were any line pressure DTC's present along with this DTC, make sure to inspect the Transmission Oil Pump and Pressure Control Solenoid.
      If DTC's P0876 and/or P0875 were present in addition to the P0731, replace the Transmission Solenoid/TRS Assembly in addition to necessary internal repairs. Pay particular attention to the following list of possible causes when repairing the transmission condition.
      Cut UD piston seal
      Failed overrunning clutch
      Faulty solenoid module
      Cut UD accumulator seal ring
      Broken UD accumulator piston
      Broken reaction shaft support seal ring
      Low line pressure
      Broken/missing main valve body bleed orifice
      Broke/missing dribbles orifice assy in reaction shafts support
      If there are no possible causes remaining, view repair.


    Repair internal transmission. Refer to appropriate AUTOMATIC TRANSMISSION article. Perform (NGC) 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .

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