Additional Wiring

For complete wiring diagrams, refer to:

SYSTEM WIRING DIAGRAMS for Compass.

SYSTEM WIRING DIAGRAMS for Patriot.

The PCM performs a continuous check of the O2 sensor 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.