P0734-GEAR RATIO ERROR IN 4TH

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 and P01736).

2) An excessive change in input or output speeds indicating signal intermittent will 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
  
LOW FLUID LEVEL
  
INPUT SPEED SENSOR OR WIRING
  
VALVE BODY ACCUMULATOR COVER FAILED
  
CUT OD OR 4C ACCUMULATOR SEAL
  
CRACKED OD OR 4C ACCUMULATOR PISTON
  
BROKEN OR MISSING OD BLEED ORIFICE IN MAIN VALVE BODY
  
CUT 4C TOWER SEAL
  
TRANSMISSION SOLENOID/TRS ASSEMBLY
  
CUT OR MISSING #5 OR #6 CHECK BALL
  
WORN SOLENOID SWITCH VALVE OR PLUGS
  
CUT OD OR 4C PISTON SEAL
  
STUCK MAIN REGULATOR VALVE
  
BURNED OD OR 4C CLUTCH
  
BROKEN OR MISSING 4C BLEED ORIFICE IN 2C/4C RETAINER
  
BROKEN REACTION SHAFT SUPPORT SEAL RING
  
POOR MACHINING ON PUMP VALVE BODY FACE
  
LOOSE / MISSING DRIBBLER ORIFICE ASSEMBLY IN REACTION SHAFT SUPPORT
  
CRACKED / LOOSE / MISSING OD/REVERSE PISTON BLEED ORIFICE
  
BROKEN REVERSE CARRIER HUB WELD
  
BROKEN REVERSE SUN GEAR WELD TO REACTION CARRIER
  

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 DTC EVENT DATA


NOTE: Make sure to record all DTC EVENT DATA stored in the scan tool for future reference in this test procedure.



Does the DTC EVENT DATA display information for the DTC P0734?

Yes
  • Go To 4


No
  • Go To 3

3.CHECK FOR ANOTHER DTC


In the DTC EVENT DATA recorded earlier, does the DTC EVENT DATA show the DTC P1790, with Target Gear = 4th, or with both the 4C and OD clutches applying?

Yes
  • Go To 4


No
  • Go To 6

4.CHECK INPUT RPM


In the DTC EVENT DATA recorded earlier, does the Input RPM read zero?

Yes
  • Refer to the Transmission category and perform the diagnostic procedure for P0715 (Input Speed Sensor Error). Diagnose the DTC as if it is set and current.


No
  • Go To 5

5.CHECK LINE PRESSURE READING


In the DTC EVENT DATA recorded earlier, is the line pressure reading more than 10 PSI below the desired line pressure reading?

Yes
  • Remove the Transmission Oil pan and check the Transmission Oil filter for improper installation or plugged, if Primary oil filter is OK, check the main regulator valve in pump. If excessive debris is in the oil pan, check clutches and repair as necessary. Refer to the Service Information for proper repair procedures.
  • Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)


No
  • Go To 6

6.CHECK TRANSMISSION FOR SLIPPAGE




During the road test, was there any obvious slippage noted in 4th gear or a runaway during the 3-4 shift?

Yes
  • Go To 8


No
  • Go To 7

7.CHECK IF DTC RESETS



Did the DTC P0734 reset?

Yes
  • Go To 8


No
  • Test Complete.

8.CHECK INTERNAL TRANSMISSION

  • Excessive debris in the oil pan.
  • Remove the Valve Body and check if the accumulator cover is intact and the 4C tower seal is not cut or split.
  • OD and 4C accumulator pistons for cracks and/or cut seals.
  • Solenoid Switch Valve and its plugs for stickiness or wear.
  • Cut or missing #5 and/or #6 check ball.
  • OD bleed orifice on top of the Valve Body
  • Air check the OD and 4C hydraulic clutch circuits for excessive leakage. Refer to the Service information.

NOTE: Both the OD and 4C hydraulic clutch circuits contain a small bleed orifice. A small amount of air leakage is considered normal. The OD hydraulic clutch circuit bleed orifice connects to the Reverse input clutch hydraulic cavity. A small amount of air leakage into the Reverse hydraulic clutch circuit is considered normal.



Were there any problems found?

Yes


No
  • Go To 9

9.CHECK REVERSE GEAR


Was there no reverse gear during the road test?

Yes (no reverse)


No (reverse gear OK)

10.CHECK ROAD TEST RESULTS


During the road test, was there no 2nd gear and no 4th gear, but 3rd gear (limp-in) was OK?

Yes


No

11.CHECK FOR BROKEN REVERSE SUN GEAR WELD






Is the reaction carrier turning faster than the drive shell?

Yes


No

12.CHECK REVERSE CARRIER HUB WELD



Were there any problems found?

Yes


No