P0734-GEAR RATIO ERROR IN 4TH

For a complete wiring diagram Refer to Section 8W

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, output speed greater than 180 rpm, no N2 - N3 input speed sensor errors present, no gear selector lever errors present, no ABS system errors, and all wheel speeds above 450 rpm.
Set Condition:
No shifting operation and detected gear is not the actual gear. No shifting operation - detected (calculated) gear is less than actual (expected) gear, no plausible gear is calculated, actual turbine speed - calculated turbine speed is greater than 300 rpm or calculated transmission ratio is above threshold. During an Upshift - detected (calculated) gear is less than actual (expected) gear. During Downshift - detected (calculated) gear is less than actual (expected) gear.

Possible Causes

LOW TRANSMISSION FLUID

OTHER TRANSMISSION DTCS PRESENT

INTERNAL TRANSMISSION FAILURE

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

Diagnostic Test

1. CHECK FOR OTHER TRANSMISSION DTCS

With the scan tool, check transmission DTCs.

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

Yes

Refer to the symptom list and perform the appropriate symptom.

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 per the Service Information. 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.

Check the transmission fluid level per the Service Information. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1/FILTER - STANDARD PROCEDURE)

Is the fluid level correct?

Yes

Go To 3

Properly adjust the fluid level per the Service Information.
Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

3. CHECK IF DTC IS CURRENT

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.

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 P0734-GEAR RATIO ERROR IN 4TH reset?

Yes

Repair internal transmission as necessary. Pay particular attention to components related to the referenced DTC. Refer to the Service Information for proper repair procedures.

Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

Go To 4

4. INTERMITTENT WIRING AND CONNECTORS

The conditions necessary to set this DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wiring and connectors while checking for any possible open or shorted circuits.
Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.

Were there any problems found?

Yes

Repair as necessary.

Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

Test Complete.