P1731-INCORRECT GEAR ENGAGED

For a complete wiring diagram Refer to Section 8W

Theory of Operation

The TCM compares the calculated gear with the gear the transmission has actually engaged. The actual gear is identified by verifying the signals of the two input speed sensors 1 (N2) and 2 (N3) as well as the transmission output speed (from the ABS system). If the actual gear differs from the gear calculated by the TCM, the TCM value is adjusted to the engaged gear and a counter is increased by 2 points. If after a shift the engaged gear and the calculated gear still match, the counter is decreased by 1 point. A DTC is detected as soon as the counter exceeds a threshold.

When Monitored:
The conditions for gear detection are: engine speed greater than 450 rpm, no input speed sensor failures are active, no selector lever error active, selector lever is not in intermediate position, selector lever position is not showing power-up value, no output speed error is active, no transfer case error is active, output speed (ABS system) greater than 180 rpm, no wheel speed (ABS system) overspeed detected.
Set Condition:
The detected gear calculated by the TCM is not identical to the actual gear. Exception: detected gear is 1st and actual gear is 2nd. If the problem is present for three consecutive ignition cycles, the TCM places the transmission into Limp-in mode until the DTC is cleared by the scan tool.

Possible Causes

TRANSMISSION SOLENOID DTCS PRESENT

ABS DTCS PRESENT

INTERNAL TRANSMISSION

TRANSMISSION CONTROL MODULE

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

Diagnostic Test

1. CHECK IF TRANSMISSION SOLENOID DTCS ARE PRESENT

With the scan tool, check for other transmission DTCs.

Are there any Transmission Solenoid DTCS present?

Yes

Refer to the symptom list and perform the appropriate symptom(s).

Go To 2

2. CHECK IF ABS DTCS ARE PRESENT

With the scan tool, check for ABS DTCs.

Are there any ABS DTCs present?

Yes

Refer to 5 - Brakes category and perform the appropriate symptom(s).

Go To 3

3. CHECK FOR INTERNAL TRANSMISSION PROBLEM

This DTC is usually set due to an internal transmission problem such as but not limited to: stuck solenoid valve and/or contamination in the valve body, broken springs, leaking clutch seals, dislodged or broken snap ring.
Inspect the internal transmission, Refer to 21- AUTOMATIC TRANSMISSION-AUTOMATIC TRANSMISSION NAG1/SERVICE INFORMATION for the appropriate service procedure(s).

Were there any problems found?

Yes

Repair as necessary.

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

Using the schematics as a guide, check the Transmission Control Module (TCM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM per the Service Information. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE - REMOVAL)
Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)