Transmission Control Module (TCM) - NAG1

P0735-GEAR RATIO ERROR IN 5TH

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Transmission Control Module (TCM) constantly calculates the transmission ratio based on the input speed sensor 1 and 2 (N2-N3) signals and the calculated output shaft speed. The intent of this diagnostic is to detect if the transmission is slipping or an invalid gear ratio is present.

- When Monitored:
Engine rpm greater than 450 rpm, no N2 - N3 input speed sensor errors present, no gear selector lever errors present, no ABS system errors, and vehicle speed above 10 km/h (6 mph).

- Set Condition:
No shifting operation and actual gear is not the target gear. No shifting operation - actual (calculated) gear is less than target (expected) gear, no plausible gear is calculated, actual (calculated) turbine speed is greater than 300 rpm or calculated transmission ratio is above threshold. During an Upshift - actual (calculated) gear is less than target (expected) gear. During Downshift - actual (calculated) gear is greater than target (expected) gear.





Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. NAG1 Pre-Diagnostic Troubleshooting Procedure.

1. CHECK FOR OTHER TRANSMISSION DTCS
1. With the scan tool, check transmission DTCs.

Are there any solenoid and/or solenoid supply voltage DTCs present?

Yes

- Diagnose and repair the DTC(s).

No

- Go To 2

2. CHECK TRANSMISSION FLUID LEVEL

NOTE: Low fluid level can be the cause of many transmission problems. Visually inspect the transmission and cooler lines for leakage and repair as necessary and adjust the fluid level. If no visual leaks are observed and the vehicle has obtained over 1610 km (1000 miles) from either new or transmission service, a fluid level check is unnecessary.

1. Check the transmission fluid level and condition.

Is the fluid level correct?

Yes

- Go To 3

No

- Properly adjust the fluid level.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test.

3. CHECK IF DTC IS CURRENT
1. With the scan tool, record the Environmental Data and erase Transmission DTCs.

NOTE: If the TCM detects and stores a DTC, the TCM also stores the vehicles operating conditions under which the DTC originally set and is located in scan tool under Environmental Data. Before erasing any stored DTCs, record any available data to assist in duplicating the conditions in which the DTC originally set.

2. Using the Environmental Data recorded earlier, test drive the vehicle while trying to duplicate the conditions in which the DTC originally set.

Did the DTC P0735-GEAR RATIO ERROR IN 5TH reset?

Yes

- Repair internal transmission as necessary. Pay particular attention to components related to the referenced DTC. Refer to the proper repair procedures.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test.

No

- Go To 4

4. 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 there any problems found?

Yes

- Repair as necessary.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test.

No

- Test Complete.