P1731

P1731-INCORRECT GEAR ENGAGED

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 DTC's PRESENT
- ABS DTC's PRESENT INTERNAL TRANSMISSION
- TRANSMISSION CONTROL MODULE

Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. Component Tests and General Diagnostics

Diagnostic Test
1. CHECK IF TRANSMISSION SOLENOID DTC's ARE PRESENT
With the scan tool, check for other transmission DTC's.
Are there any Transmission Solenoid DTC's present?
YES >>Refer to the Transmission category and perform the appropriate symptom(s).
NO >>Go To 2

2. CHECK IF ABS DTC's ARE PRESENT
With the scan tool, check for ABS DTC's.
Are there any ABS DTC's present?
YES >>Refer to BRAKES - ABS ELECTRICAL DIAGNOSTICS category and perform the appropriate symptom. Testing and Inspection
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. Transmission Verification Test
NO >> 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 internal transmission.
Were there any problems found?
YES >>Repair internal transmission as necessary.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. Transmission Verification Test
NO >>Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. Transmission Verification Test