DTC P0161-O2 Sensor 2/2 Heater Performance: Notes

Fig 1: O2 Sensor 2/2 Circuit - Circuit Diagram

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

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

Theory of Operation 

This diagnostic provides a continuous check of the O2 heater circuit during operation. The heater circuit is momentarily disabled to allow a resistance measurement to be taken to infer heater temperature. The current delivery to the heater is duty cycled to maintain a specific target temperature. The error from the target temperature is continuously monitored to assess heater performance. 

• When Monitored: 

  Engine running and heater duty cycle greater than 0%. Battery voltage greater than 11.0 volts. 

• Set Condition: 

  No sensor output is received when the PCM powers up the sensor heater. Two trip fault. Three good trips to turn off the MIL. 

Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding.