Originally Posted by Mitsubishi Mirage Service Manual section 23A page 33
DTC P0720: Malfunction of Output Speed Sensor
DIAGNOSTIC FUNCTION
The TCM determines whether the system is defective by monitoring the output speed sensor.
DESCRIPTIONS OF MONITOR METHODS
The status with the secondary pulley speed of 1,500 r/min or more and with the output shaft speed of 150 r/min or less continues for 10 seconds.
When the output shaft speed has dropped abruptly from 730 r/min or more to 90 r/min or less, and then it keeps 90 r/min or less for 0.5 seconds continuously.
MONITOR EXECUTION
Transmission range: D, R or B
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
P0705: Malfunction of transmission range switch
P0791: Malfunction of secondary pulley speed sensor
Sensor (The sensor below is determined to be normal)
Transmission range switch
Secondary pulley speed sensor
DTC SET CONDITIONS
Check Conditions
Transmission range switch position: D, R or B.
Voltage of battery: 10 volts or more.
Voltage of battery: 16.5 volts or less.
Judgment Criteria
The status with the secondary pulley speed of 1,500 r/min or more and with the output shaft speed of less than 150 r/min continues for 10 seconds.
The output speed has dropped abruptly from 730 r/min or more to 90 r/min or less. Then at least 0.5 seconds have passed with the reduced speed.
OBD-II DRIVE CYCLE PATTERN
The vehicle is driven for at least 20 seconds with the engine speed at 3,500 r/min or more.
PROBABLE CAUSES
Malfunction of output speed sensor
Damaged wiring harness and connectors
Malfunction of TCM