P1D9C

P1D9C-INCORRECT GEAR RATIO: CLUTCH A OR C DEFECTIVE

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.

- Set Condition:
After a calibrated number of failure symptoms are detected, a DTC is stored and the Transmission Control Module (TCM) commands a calibrated default gear. This gear is monitored as well and if a failure is detected for this gear, an alternative default gear is engaged and so on. The selection of alternative default gears follows a calibrated logic. This logic will detect a damaged clutch and to finally select an alternative gear that consists of a combination of clutches in which the damaged clutch is not involved. If a further failure symptom occurs in this final alternative default gear, a failure for general transmission ratio malfunction is stored.





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.