Transmission Control Module (TCM) - 8HP45

P0730-INCORRECT GEAR RATIO

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 fix 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 output speed and the output speed gradient must be higher than a calibrated threshold.

- Set Condition:
The Transmission Control Module (TCM) did not detect a gear ratio change when commanded.





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 CONTROL MODULE ASSEMBLY (TCMA)

If there are no possible causes remaining, view repair.

Repair

- Using the schematics as a guide, check the TCMA terminals for corrosion, damage or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the TCMA. Valve Body - Removal.
- 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.