P0731
DTC P0731: 1st Gear Incorrect Ratio
DESCRIPTIONS OF MONITOR METHODS
- After 1st gear is achieved for 2 seconds, the abnormal gear ratio*1 is detected for 2 seconds continuously, or the engine run-up*2 is detected for 250 milliseconds.
*1: The actual gear ratio deviates from the target gear ratio to the low engine (turbine) speed.
*2: The actual gear ratio deviates from the target gear ratio to the high engine (turbine) speed.
MONITOR EXECUTION
- 1st gear driving
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- P0846: Malfunction of the 2-6 brake pressure switch system
- P0876: Malfunction of the High clutch pressure switch system
- P0988: Malfunction of the Low-reverse brake pressure switch system
Sensor (The sensor below is determined to be normal)
- Input shaft speed sensor
- Output shaft speed sensor
- Transmission range switch
- Lock-up and low-reverse brake linear solenoid
- Low clutch linear solenoid
- 2-6 brake linear solenoid
- 3-5 reverse clutch linear solenoid
- High clutch linear solenoid
- Low clutch shift solenoid
- Low-reverse brake shift solenoid
- Engine revolution signal
- CAN communication
LOGIC FLOW CHARTS (Monitor Sequence)
DTC SET CONDITIONS
Check Conditions
- Shift stage: 1st gear.
- Time after shift changing finish: 2 seconds or more.
Judgement Criteria
- Gear ratio: 4.978 or more. (0.25 second)
- Gear ratio: 2.114 or more and 2.584 or less. (2 seconds)
- Gear ratio: 1.392 or more and 1.701 or less. (2 seconds)
- Gear ratio: 1.021 or more and 1.247 or less. (2 seconds)
OBD-II DRIVE CYCLE PATTERN
1st gear driving for 5 seconds or more
TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CODE TO BE SET ARE:)
- Transaxle assembly powertrain parts failure
- Malfunction of the P0715: input shaft speed sensor system
- Malfunction of the P0720: output shaft speed sensor system
- Malfunction of the P0748: line pressure linear solenoid valve system circuit
- Malfunction of the P0753: low clutch linear solenoid valve system circuit
- Malfunction of the P1758: low-reverse brake shift solenoid valve system circuit
- Malfunction of the low clutch
- Malfunction of the low one-way clutch
- Malfunction of the valve body assembly
DIAGNOSIS
STEP 1. Check the DTC.
Check that P0715 (input shaft speed sensor) and P0720 (output shaft speed sensor) are set.
Q. Is the DTC set?
YES Check and repair the relevant DTC system.
NO Go to Step 2.
STEP 2. Check the DTC.
Check if the DTC other than P0731 (1st gear ratio) is set.
Q. Is the DTC set?
YES Check and repair the relevant DTC system.
NO Go to Step 3.
STEP 3. Check the transmission fluid properties.
Check the status of the transmission fluid properties (smell, color, fouling).
- Black: A/T inside damage, seizure
- Milky: Water intrusion
Q. Is the check result normal?
YES Go to Step 4.
NO Remove the A/T from the vehicle, then check and repair the inside.
STEP 4. Check the transmission fluid level.
Q. Is the check result normal?
YES Go to Step 5.
NO Adjust the transmission fluid level, and then go to Step 5.
STEP 5. Check the signals of input shaft speed sensor and output shaft speed sensor.
Check the signals of C-37 TCM connector terminal No. 37 and No. 38.
Refer to Automatic Transmission.
Q. Is the check result normal?
YES Go to Step 6.
NO Repair or replace the failure section.
STEP 6. Hydraulic pressure test
Refer to Hydraulic Pressure Test.
Q. Is the check result normal?
YES Go to Step 7.
NO Remove the A/T from the vehicle, then check and repair the inside.
STEP 7. Erase the DTC code, and drive the vehicle for a while.
Check that the normal code is displayed.
Q. Is the check result normal?
YES The procedure is complete.
NO Return to START.