P0731
DTC P0731: 1st Gear Incorrect RatioDESCRIPTIONS 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
^ Continuous
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
^ DTC P0705: Transmission range switch malfunction
^ DTC P0715: Input shaft speed sensor malfunction
^ DTC P0720: Output shaft speed sensor malfunction
^ DTC P0743: Lock-up and low-reverse brake linear solenoid malfunction
^ DTC P0753: Low clutch linear solenoid malfunction
^ DTC P0758: 2-6 brake linear solenoid malfunction
^ DTC P0763: 3-5 reverse clutch linear solenoid malfunction
^ DTC P0768: High clutch linear solenoid malfunction
^ DTC P1753: Low clutch shift solenoid malfunction
^ DTC P1758: Low-reverse brake shift solenoid malfunction
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)
Logic Flow Charts (Monitor Sequence):
DTC SET CONDITIONS
Check Conditions
^ Shift stage: 1st gear.
^ Time after shift changing finish: more than 2 seconds.
Judgement Criteria
^ Gear ratio: more than 4.978. (0.25 second)
^ Gear ratio: more than 2.114 and less than 2.584. (2 seconds)
^ Gear ratio: more than 1.392 and less than 1.701. (2 seconds)
^ Gear ratio: more than 1.021 and less than 1.247. (2 seconds)
OBD-II DRIVE CYCLE PATTERN
Start the engine, and drive at more than 20 km/h (12 mph) for 10 seconds, with 1st gear fixed (1st gear in sport mode).
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.
Q:Is the check result normal?
YES: Go to Step 6.
NO: Repair or replace the failure section.
STEP 6. 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.