Oxygen Sensor (O2S) Monitor

As Oxygen Sensor signal switches, PCM monitors half cycle and big slope signals from oxygen sensor. If during test neither counter reaches a predetermined value, a malfunction is entered and a Freeze Frame is stored. Only one counter reaching its predetermined value is needed for monitor to pass.

The Oxygen Sensor Monitor is a 2 trip monitor that is tested only once per trip. When Oxygen Sensor fails test in 2 consecutive trips, MIL is illuminated and a DTC is set. The MIL is extinguished when Oxygen Sensor monitor passes in 3 consecutive trips. The DTC is erased from memory after 40 consecutive warm-up cycles without test failure.

Enabling Condition -  The following conditions must typically be met for PCM to run oxygen sensor monitor:

• Battery Voltage
• Engine Temperature
• Engine Run Time
• Engine Run Time At A Predetermined Speed
• Engine Run Time At A Predetermined Speed And Throttle Opening
• Transmission In Gear And Brake Depressed (Automatic Only)
• Fuel System In Closed Loop
• Long Term Adaptive (Within Parameters)
• Power Steering Switch In Low PSI (No Load)
• Engine At Idle
• Fuel Level Above 15%
• Ambient Air Temperature
• Barometric Pressure
• Engine RPM Within Acceptable Range Of Desired Idle

Pending Condition -  The Task Manager typically does not run Oxygen Sensor Monitor if overlapping monitors are running or MIL is illuminated for any of the following:

• Misfire Monitor
• Front Oxygen Sensor and Heater Monitor MAP Sensor
• Vehicle Speed Sensor
• Engine Coolant Temperature Sensor
• Throttle Position Sensor
• Engine Controller Self Test Faults
• Cam or Crank Sensor
• Injector and Coil
• Idle Air Control Motor
• EVAP Electrical
• EGR Solenoid Electrical (if equipped)
• Intake Air Temperature
• 5 Volt Feed

Conflict -  The Task Manager does not run Oxygen Sensor Monitor if any of the following conditions are present:

• A/C On (A/C Clutch Cycling Temporarily Suspends Monitor)
• Purge Flow In Progress
• Ethanol Content Learn Is Taking Place And The Ethanol Used Once Flag Is Set

Suspend -  The Task Manager suspends maturing a fault for Oxygen Sensor Monitor if an of the following are present:

• Oxygen Sensor Heater Monitor, Priority 1
• Misfire Monitor, Priority 2