The value of the input shaft speed should be equal to the value of the output shaft speed, when multiplied by the 1st gear ratio, while the transaxle is engaged in the 1st gear. For example, if the output speed is 1000 rpm and the 1st gear ratio is 2.919, then the input speed is 2.919 rpm.
This code is set if the value of input shaft speed is not equal to the value of the output shaft, when multiplied by the 1st gear ratio, while the transaxle is engaged in 1st gear. This malfunction is mainly caused by mechanical troubles such as control valve sticking or solenoid valve malfuctioning rather than an electrical issue.
Item
Detecting Condition
Possible Cause
DTC Strategy
1st gear incorrect ratio
Faulty Input speed sensor
Faulty output speed sensor
Faulty UD clutch or LR brake or Oneway clutch
Enable Conditions
Engine speed >400rpm
Output speed >200rpm
Input speed >300rpm
Monitoring time > 4
Threshold Value
Output speed <(input speed-200rpm)/1st. gear ratio
Diagnostic Time
More than 1sec.
Fail Safe
Locked into 3 rd gear.(If diagnosis code P0731 is output four times, the transaxle is locked into 3rd gear)
Input shaft & Output shaft speed sensor
Type : Hall sensor
Current consumption : 22mA(MAX)
Sensor body and sensor connector have been unified as one.
Fig 1) INPUT SIGNAL ? LOW SPEED
Fig 2) INPUT SIGNAL ? HIGH SPEED