P0720-Output Speed Sensor Circuit: Notes

Fig 1: Output Speed Sensor Circuit Diagram

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

For a complete wiring diagram  , refer to appropriate SYSTEM WIRING DIAGRAMS article.

Theory of Operation 

The transmission system uses two speed sensors, one to measure input RPM and one to measure output RPM. These inputs are essential for proper transmission operation. Therefore, the integrity of this data is verified through the following checks: 

1. When in gear, if the gear ratio does not compare to a known gear ratio, the corresponding in-gear trouble code is set (codes P0731 through P0736). 
2. An excessive change in input or output speeds indicating signal intermittent will result in codes P0715 and/or P0720 being set. 
3. If the common speed sensor ground circuit is lost, both sensor inputs will read the signal from the input speed sensor at idle in neutral. Since the input speed sensor has 60 teeth and the output speed sensor has 30 teeth, this results in an apparent speed ratio of 1:2 and may cause the DTC P1794 to set. 
   • When Monitored: 

     The transmission gear ratio is monitored continuously while the transmission is in gear. 

   • Set Condition: 

     If there is an excessive change in output RPM in any gear. This DTC can take up to five minutes of problem identification before illuminating the MIL. 

Always perform the 45RFE/545RFE PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding.