P1731-INCORRECT GEAR ENGAGED
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 trying to mechanically shift into a different gear than the TCM intends.
| NOTE: | The transmission control module is programmed to immediately place the transmission into neutral if P0730 or P1731 codes are set. These codes indicate that the transmission experienced an unknown or incorrect gear ratio. Placing the transmission in neutral prevents potential catastrophic failure. When this occurs, the transmission will remain in neutral until the vehicle slows to 29 Km/h (18 mph). |
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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).
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Set Condition:
No shifting operation and actual gear differs from the target gear. No shifting operation - actual (calculated) gear differs from target (expected) gear, 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. Exception: Actual (calculated) gear is 1st and target (desired) gear is 2nd.
Possible Causes |
|---|
| LOW FLUID LEVEL |
| ABS DTCS PRESENT |
| TRANSMISSION SOLENOID, SPEED SENSOR AND/OR OTHER ELECTRICAL RELATED DTCS PRESENT |
| INTERMITTENT STICKING VALVE IN THE VALVE BODY |
| INTERNAL TRANSMISSION PROBLEM |
| TRANSMISSION CONTROL MODULE (TCM) |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).
1. CHECK IF ABS DTCS ARE PRESENT
| 1. | With the scan tool, check for ABS DTCs. |
Are there any ABS DTCs present?
Yes
- (Refer to 28 - DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Diagnosis and Testing) and perform the appropriate diagnostic procedure.
No
- Go To 2
2. CHECK IF TRANSMISSION SOLENOID DTCS ARE PRESENT
| 1. | With the scan tool, check for other transmission DTCs. |
Are there any transmission solenoid, speed sensor and/or any other transmission electrical related DTCs present?
Yes
- (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Diagnosis and Testing) and perform the appropriate diagnostic procedure.
No
- Go To 3
3. 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 in accordance with 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. |
| 1. | Check the transmission fluid level and condition in accordance with the Service Information. |
Is the fluid level correct?
Yes
- Go To 4
No
- Correct the fluid level in accordance with the Service Information. (Refer to 21 - Transmission and Transfer Case/Automatic - NAG1/FLUID and FILTER - Standard Procedure) .
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).
| 1. | With the scan tool, check environmental data for P1731. |
Did the environmental data show the code setting during a 3-4 upshift or 4-3 downshift?
Yes
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NOTE: Debris may enter through the vents in the top of the valvebody. The debris can be a very small sliver that is visibly unnoticable unless flushing onto a fine filter paper. The debris has the potential to stick the 3-4 Shift Pressure or 3-4 Holding valves. If either valve is stuck during a 3-4 upshift or 4-3 downshift, a shift flare, bump shift, harsh shift, or neutraling out will occur. - Flush and clean the Valve Body in accordance with the Service Information. (Refer to 21 - Transmission and Transfer Case/Automatic - NAG1/UNIT, Electrohydraulic Control - Cleaning) . Pay particular attention to the 3-4 shift pressure and 3-4 holding valve.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).
No
- Go To 5
5. CHECK FOR INTERNAL TRANSMISSION PROBLEM
| 1. | Check for an internal Transmission mechanical problem(s). |
| 2. | Remove the Transmission Oil Pan and inspect for excessive debris or a plugged Transmission Oil Filter. (Refer to 21 - Transmission and Transfer Case/Automatic - NAG1/FLUID and FILTER - Standard Procedure) . |
| 3. | Inspect the valve body for foreign material, starting with the four valves associated with the shift described in the environmental data (shift pressure, holding, overlap, command), and continue on to the other valves. |
| 4. | 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 etc. |
| 5. | Inspect the internal transmission. |
Were there any problems found?
Yes
- Repair as necessary in accordance with the Service Information.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).
No
- 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 and program the TCM in accordance with the Service Information.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).