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