DTC Advanced Diagnostics: P0731
DTC P0731 : 1st Gear Incorrect Ratio
General Description
Two-way clutch position required to shift in each shift position/mode
| Shift position/mode | One-way clutch function | Lock function |
|---|---|---|
| P | YES | YES |
| R | NO | YES |
| N | YES | YES |
| D (1st gear*) | YES | YES |
| D (2nd to 10th gear) | YES | NO |
*: Possible to shift regardless of the two-way clutch position
The two-way clutch switches forward and reverse by switching to one-way clutch function that idles one side and lock function that disables idle both sides. The two-way clutch switches forward and reverse by driving two-way clutch actuator valve with shift solenoid valves A, B, and D, and clutch pressure control solenoid valve B. The two-way clutch switching position is monitored by the two-way clutch actuator valve stroke sensor which measures the stroke position of the two-way clutch actuator valve. The two-way clutch position that is required to shift in each shift position/mode is shown in the table. The detection is performed to guarantee the vehicle start in case the gear changes to neutral that is expected to be 1st gear due to the malfunction of one-way clutch function. If the value difference between the mainshaft speed sensor and the countershaft speed sensor is a specified value when steady driving at 1st gear and actual torque converter slip rate is in a specified range and the value of transmission fluid pressure sensor F is a specified value for a specified time, the transmission control module (TCM) determines the condition as neutral when it is expected to be 1st gear and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 2 seconds or more |
| DTC Type | Two drive cycles, MIL off, shift position indicator blinks |
Enable Conditions
| Condition | Minimum | Maximum | |
|---|---|---|---|
| Engine speed [Engine Speed] | 500 rpm | - | |
| 12 volt battery voltage [Battery Voltage] | 10 V | - | |
| Other | Steady driving at 1st gear | ||
[ ]:HDS Parameter
Malfunction Threshold
All of the following conditions are established for at least 2 seconds:
- The value difference between the mainshaft speed sensor value and countershaft speed sensor value multiplied by the 1st gear ratio is greater than 300 rpm.
- Actual torque converter slip rate is 83 % or more, or 110 % or less when the vehicle is stopped or actual torque converter slip rate is 96 % or more, or 110 % or less when the vehicle is driven.
- Transmission fluid pressure sensor F value is 350 kPa (3.57 kgf/cm 2, 50.8 psi) or more.
Possible Cause
- Transmission internal failure (two-way clutch)
- Countershaft speed sensor failure
Confirmation Procedure
Operating Condition
- Start the engine.
- While pressing the brake pedal, shift the transmission to D position/mode, and wait for at least 10 seconds.
- Test-drive the vehicle in 1st gear for at least 10 seconds.
- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the TCM memory. If the malfunction returns in the next (second) drive cycle, the shift position indicator blinks and a Confirmed DTC and the freeze data are stored. The MIL does not come on.
Conditions for clearing the DTC
The shift position indicator comes off by turning the vehicle to the OFF (LOCK) mode. The Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool clear command.