P1DB4
P1DB4-INCORRECT GEAR RATIO DURING GEAR ENGAGEMENT OR IN GEAR
For a complete wiring diagram Refer to the Wiring Information.
Theory of Operation
The purpose of the diagnostic is to detect malfunctions which lead to an unexpected transmission ratio (e.g. slipping clutches, hydraulic or mechanical defects, etc.). The monitoring is done by an out-of-range check by comparing the actual gear ratio (i.e. the ratio of input speed to output speed) to a minimum and maximum calibrated gear ratio threshold. The function monitors the gear ratio while driving in a fixed gear, during gear engagement and during shifting from one gear to another.
- When Monitored:
Driving position is in Drive or Reverse.
Oil temperature above a calibrated threshold.
No clutch slip control functions commanded.
No failure in input speed signal.
Input speed above a calibrated threshold.
Valid output speed signal from the output speed sensor or calculated from the wheel speed signal if output speed sensor is not available.
Valid engine speed signal from the PCM.
The absolute value of the input speed gradient and pedal position must be lower than their respective calibrated thresholds.
- Set Condition:
If the output speed is greater than a calibrated threshold, a failure is detected when the measured gear ratio exceeds the specific gear ratio range which is depending on the ratio at the beginning of the gear engagement for a calibrated amount of time. If the output speed is lower than this calibrated threshold, a failure is detected if the input speed difference (difference between the actual input speed and the input speed at the beginning of the monitoring) exceeds a calibrated threshold for a period of time. If a failure is detected during gear engagement, the Transmission Control Module (TCM) aborts the gear engagement and changes to a neutral position. After a calibrated number of failures a DTC is stored and on the next request for gear engagement, the TCM will command a default gear.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 8HP45 Pre-Diagnostic Troubleshooting Procedure
1. CHECK IF DTC IS CURRENT
NOTE: The Transmission Control Module stores under Environmental Data the transmission operating conditions when the DTC was set. Before clearing any DTCs, record all information pertaining to the DTC.
1. With the scan tool, CLEAR transmission DTCs.
2. Using the Environmental Data previously recorded, drive the vehicle and try to duplicate the condition in which the DTC set.
Does the DTC reset?
Yes
- Go To 2
No
- Go To 3
2. TRANSMISSION
If there are no possible causes remaining, view repair.
Repair
- If the DTC returns, replace the transmission Removal Perform the appropriate repair for this DTC.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.
3. INTERMITTENT WIRING AND CONNECTORS
1. The conditions necessary to set this DTC are not present at this time.
2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
3. Wiggle the wiring and connectors while checking for any possible open or shorted circuits.
4. Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.
No
- Test Complete.