68RFE Automatic Transmission
P0732-GEAR RATIO ERROR IN 2ND
For a complete wiring diagram refer to Diagrams/Electrical. Electrical Diagrams
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:
NOTE: Various Gear Ratio Error DTCs will set only if the transmission slips after first achieving the correct ratio. Therefore, a transmission with no drive (or reverse) may not set any Gear Ratio Error DTC because it never achieves a correct gear ratio.
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 P0729 and P0731-36).
2) An excessive change in input or output speeds indicating signal intermittent will result in the DTCs P0716 and/or P0721 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
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 68RFE Pre-Diagnostic Troubleshooting Procedure
Diagnostic Test
1. CHECK FOR RELATED DTCS
With the scan tool, check for other transmission DTCs.
Are there any Transmission: solenoid, line pressure, speed sensor, and/or loss of prime DTCs present?
Yes
- Refer to appropriate symptom in the Transmission category. Perform the test for P0944-LOSS OF PRIME first if it is present. P0944
No
- Go To 2
2. CHECK IF DTC IS CURRENT
With the scan tool, read and record the 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 P0732?
Yes
- Go to4
No
- Go to3
3. CHECK DTC EVENT DATA
In the DTC EVENT DATA, identify the DTC that was recorded earlier.
Does the DTC EVENT DATA display information for the DTC P1790, with target gear = 2nd, or with both 2C and UD clutches applying?
Yes
- Go to4
No
- Go to7
4. CHECK RPM IN DTC EVENT DATA
Refer to the DTC EVENT DATA recorded earlier.
Does the Input rpm read zero?
Yes
- Check the input speed sensor and wiring. Refer to test P0716 and diagnose as if the DTC is current. P0716
No
- Go to5
5. CHECK LINE PRESSURE READING
Refer to the DTC EVENT DATA recorded earlier.
Is the line pressure reading more than 10 psi below the desired line pressure?
Yes
- Go to6
No
- Go To7
6. CHECK TRANSMISSION OIL FILTER
Turn the ignition off to the lock position.
Remove and inspect the Transmission Oil Pan for excessive debris.
Remove and inspect the Primary Oil Filter.
NOTE: Make sure the Primary Transmission Oil Filter and seal are properly installed and are not cracked or split.
Does the Oil Pan contain excessive debris and/or is the Primary Oil Filter cracked, plugged or mis-installed?
Yes
- Repair the plugged, cracked, or split Primary Transmission Oil Filter and/or seal. If excessive clutch debris is present, check the clutches for damage.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Remove the Transmission Oil Pump. Check the main Regulator Valve for sticking in its bore, scoring, and/or damage and clean and repair as necessary. If no problem is found, replace the Transmission Solenoid/TRS Assembly.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
7. CHECK IF THE DTC P0732 IS CURRENT
With the scan tool, perform the 2nd Gear Clutch Test. Follow the instructions on the scan tool.
Increase the throttle angle, TPS Degree, to 30� for no more than a few seconds.
CAUTION: Do not overheat the transmission.
NOTE: If the 2C clutch is faulty, the overrunning clutch will hold and the slip test will pass. The 2nd gear clutch test will not detect a faulty 2C clutch. However, it will detect a faulty UD clutch.
Did the clutch test pass, did the Input Speed remain at zero?
Yes
- Go to8
No
- Go To 10
8. CHECK FOR INTERMITTENT OPERATION
Check the Shifter 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 Ignition Switch Feed fuse from the TIPM.
CAUTION: Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear.
WARNING: The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in personal injury or death.
Check the Speed Sensor wiring and connectors for good connection, then perform a wiggle test using the Transmission Simulator, Miller tool #8333.
Were there any problems found?
Yes
- Repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Go to9
9. CHECK FOR SLIPPAGE
With the scan tool, erase Transmission DTCs.
Road test the vehicle.
Does the Transmission fail to make a 1-2 upshift (stays in 1st gear and then shifts to direct gear), or is there obvious slippage noticed in 2nd gear?
Yes
- Go To 12
No
- Go To 16
10. CHECK THE UD HYDRAULIC CLUTCH CIRCUIT
Remove Transmission Oil Pan and check for excessive debris.
Remove the Valve Body and air check the UD hydraulic clutch circuit (in the case).
NOTE: The UD clutch passage contains a small bleed orifice, a small amount of air leakage is normal.
Were there any problems found, excessive debris and/or excessive air leakage in the UD clutch hydraulic circuit?
Yes
- Repair as necessary. Check the UD clutch piston seals, reaction shaft support seal rings and the dribbler assembly, and the flatness of the pump valve body and pump housing faces. Check main regulator valve for sticking in the bore.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Go To 11
11. CHECK THE UD ACCUMULATOR PISTON
Check the UD bleed orifice, accumulator piston, and accumulator piston seal in the main valve body.
Were there any problems found?
Yes
- Repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Replace Transmission Solenoid/TRS Assembly.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
12. CHECK FOR EXCESSIVE DEBRIS
Remove the Transmission Oil Pan and check for excessive debris.
If grey sludge is present, check for a improperly assembled 2C clutch with the thick reaction plate not against the case.
Remove the valve body and air check the 2C hydraulic clutch circuit (in the 2C/4C clutch retainer).
NOTE: The 2C clutch passage contains a small bleed orifice, a small amount of air leakage is normal.
Were there any problems found, excessive debris, improperly assembled 2C clutch and/or excessive air leakage in the 2C hydraulic clutch circuit?
Yes
- Repair as necessary. Note: Check the 2C piston seals and bleed orifice.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Go To 13
13. CHECK THE 2C ACCUMULATOR
Check the 2C Accumulator piston for cracks or a cut seal.
Check for a cut or missing #7 or #5 check ball.
Check the Solenoid Switch Valve and its plugs for sticking in its bore or excessive wear.
Were there any problems found
Yes
- Repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Go To 14
14. CHECK FOR FAILED REVERSE GEARSET SPLINES
Working through the windows in the bottom of the case, check for a failed Reverse Sun or Annulus spline as follows:
1) Hold the Transmission Output Shaft by holding the Transmission Manual Lever in the park position.
2) Apply the 4C clutch using 30-40 psi shop air at the apply port in the center bulkhead.
3) Attempt to rotate the input annulus gear and drive shell (the drum that encloses the two rearmost gearsets).
NOTE: Due to the overrunning clutch, the gear and drive shell normally rotates in one direction only.
Can the drive shell be rotated?
Yes
- Repair internal transmission as necessary. Check the reverse annulus gear spline to the input carrier, and the reverse sun gear spline to the reaction carrier hub.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Go To 15
15. CHECK THE DRIVE SHELL WELD
Release the output shaft and the 4C clutch.
Apply the L/R Clutch only using 30-40 psi of shop air.
Attempt to rotate the drive shell as in the previous step.
Can the drive shell be rotated?
Yes
- Repair Transmission as necessary. Check the drive shell weld to input annulus gear.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Replace the Transmission Solenoid/TRS Assembly.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
16. CHECK IF DTC RESETS
Did the DTC P0732 reset during the road test?
Yes
- Go To 17
No
- Go To 18
17. LIST OF POSSIBLE CAUSES
If any other DTCs set during the road test, refer to the appropriate symptom in the Transmission category.
If no other DTCs set during the road test, below is a list of possible causes, but not strictly limited to those:
- Check for excessive debris in the Transmission Oil pan, plugged, cracked, or misinstalled Primary Transmission Oil Filter and/or seal.
- Check for cut and/or missing #7 and #5 check balls in the main valve body.
- Check the 2C and UD accumulator pistons and seals, UD bleed orifice, and the Solenoid Switch Valve and Plugs in the main valve body.
- Check the UD clutch piston seals, reaction shaft support seal rings and dribbler assembly.
- Check the 2C clutch piston seals, and bleed orifice.
- Check the main regulator valve for sticking in its bore and the flatness of the pump valve body and pump housing faces.
- Check for a improperly assembled 2C clutch with the thick reaction plate not against the case.
View repair
Repair
- Repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
18. INTERMITTENT DTC
The conditions to set this DTC are not currently present.
With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.
- If the DTC Event Data shows fault P0732 was set in Park, Reverse, or Neutral, replace the Powertrain Control Module.
- If the DTC Event Data shows fault P0732 set with input rpm = zero, check the input speed sensor and related wiring.
- If the DTC Event Data shows fault P0732 set with line pressure significantly below desired line pressure, check for the cause of low line pressure (i.e., oil level, misinstalled or damaged primary filter or filter seal, sticking main regulator valve in pump, etc.).
- If the DTC Event Data shows fault P0732 set with the UD or 2C pressure switch open (but line pressure matches Desired Line Pressure), air check the UD and 2C hydraulic clutch circuits for leakage. If the UD and 2C hydraulic clutch circuits are OK, replace the Transmission Solenoid/TRS 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 Ignition Switch Feed fuse from the TIPM.
CAUTION: Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear.
WARNING: The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in personal injury or death.
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.
Verify if the problem is only experienced under extreme hot or cold conditions.
Were there any problems found.
Yes
- Repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Test Complete.