P0731-GEAR RATIO ERROR IN 1ST

For a complete wiring diagram Refer to Section 8W

Theory of Operation


The 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 the following checks:

1) Once in a particular gear, if the gear ratio varies from the correct gear ratio, the corresponding in-gear trouble code is set (DTCs P0731–36).

2) An excessive change in input or output speeds indicating signal intermittent may result in the DTCs P0715 and/or P0720 being set.

3) If the common speed sensor ground circuit is lost, both sensor inputs will read the pulses from the input speed sensor when at a stop in neutral. Since the input speed sensor reads 60 teeth from the input clutch hub and the output speed sensor reads 30 teeth from the park gear, the result is an apparent speed ratio of 1:2 and may cause the DTC P1794 to set.


  • When Monitored:

    Continuously with the ignition on, engine running, with the transmission 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


Possible Causes
  
CUT UD PISTON SEAL
  
LOW FLUID LEVEL
  
CRACKED OR MIS-INSTALLED PRIMARY OIL FILTER OR SEAL
  
STUCK OR STICKING MAIN REGULATOR VALVE
  
FAILED OVERRUNNING CLUTCH
  
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
  
BROKEN / MISSING DRIBBLER ORIFICE ASSEMBLY IN REACTION SHAFT SUPPORT
  
POOR MACHINING ON PUMP VALVE BODY FACE
  
INPUT SPEED SENSOR AND RELATED WIRING
  
TRANSMISSION SOLENOID/TRS ASSEMBLY
  
TRANSMISSION CONTROL MODULE
  

Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)



Diagnostic Test

1.CHECK FOR RELATED DTCS




Are there any Transmission; solenoid, line pressure, speed sensor, and/or loss of prime DTCs present?

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.


No
  • Go To 2

2.CHECK IF DTC P0731 IS CURRENT



CAUTION: Do not overheat the transmission.



Did the Clutch Test pass, Input Speed remain at zero?

Yes
  • Go To 3


No
  • Go To 4

3.CHECK FOR INTERMITTENT OPERATION


  • If the DTC Event Data shows fault P0731 was set in Park, Reverse, or Neutral, replace the Powertrain Control Module.
  • If the DTC Event Data shows fault P0731 set with input RPM = zero, check the 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 the cause of low line pressure (i.e., oil level, mis-installed or damaged primary filter or filter seal, sticking main regulator valve in pump, etc.).
  • If the DTC Event Data shows fault P0731 set with the UD pressure switch open (but line pressure matches Desired Line Pressure), air check the UD hydraulic clutch circuit for leakage per the Service Information. If the UD hydraulic clutch circuit is OK, replace the solenoid/TRS assembly.




CAUTION: Removal of the Starter Relay will prevent the vehicle from being started in gear.


WARNING: The Starter Relay must be removed from the PDC. Failure to do so can result in personal injury or death.


NOTE: Failure to remove the Starter Relay can cause a Transmission - No Response condition.







Were there any problems found.

Yes


No
  • Test Complete.

4.CHECK INTERNAL TRANSMISSION




  • Cut UD piston seal
  • Failed overrunning clutch
  • Cut UD accumulator seal ring
  • Broken UD accumulator piston
  • Low line pressure
  • Broken/missing main valve body bleed orifice
  • Broken/missing dribbler orifice assembly in reaction shaft support
  • Poor machining on pump valve body face
  • Transmission Solenoid/TRS Assembly


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Repair