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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 runup*2 is detected for 2 seconds.
*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: 2-6 brake pressure switch system
  • P0876: High clutch pressure switch system
  • P0988: 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.
Judgment Criteria
  • Gear ratio: 5.097 or more. (2 seconds)
  • Gear ratio: 2.165 or more and 2.646 or less. (2 seconds)
  • Gear ratio: 1.425 or more and 1.742 or less. (2 seconds)
  • Gear ratio: 1.045 or more and 1.277 or less. (2 seconds)
 
 
OBD-II DRIVE CYCLE PATTERN
1st gear driving for 5 seconds or more
 
 
PROBABLE CAUSES
  • Transaxle assembly powertrain parts failure
  • When the DTC P0715: Input shaft speed sensor system is stored
  • When the DTC P0720: Output shaft speed sensor system is stored
  • When the DTC P0962, P0963: Line pressure linear solenoid valve system is stored
  • When the DTC P0973, P0974: Low clutch linear solenoid valve system is stored
  • When the DTC P099B, P099C: Low-reverse brake shift solenoid valve system is stored
  • 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.
Is the DTC stored?
Check and repair the relevant DTC system.
Go to Step 2.
 
STEP 2. Check the DTC.
Check if the DTC other than P0731 (1st gear ratio) is stored.
Is the DTC stored?
Check and repair the relevant DTC system.
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
Is the check result normal?
Go to Step 4.
Remove the A/T from the vehicle, then check and repair the inside.
 
STEP 4. Check the transmission fluid level.
Is the check result normal?
Go to Step 5.
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 TCM connector PGA1, PGB1 terminal.
Refer to .
Is the check result normal?
Go to Step 6.
Repair or replace the failure section.
 
STEP 6. Hydraulic pressure test
Refer to .
Is the check result normal?
Go to Step 7.
Remove the A/T from the vehicle, then check and repair the inside.
 
STEP 7. Erase the DTC, and drive the vehicle for a while.
Check that the normal code is displayed.
Is the check result normal?
The procedure is complete.
Return to Step 1.