About Monitored Circuits

- Input Signal Voltage - The PCM can determine if the circuit is open or shorted by comparing the input signal to the established range.

- Output Device Current Flow - The PCM senses whether the output device circuit is open, shorted to ground, or shorted to voltage.


- Oxygen Sensor Switching - The PCM can determine if the oxygen sensor is switching between rich and lean, once the system has entered closed loop. SEE Computers and Control Systems/Description and Operation for an explanation of Closed Loop Operation.