Oxygen Sensor (O2S) Monitor: Operation

WARNING: This page is about a different car, the 2004 Dodge Intrepid, 2004 Chrysler Intrepid, 2004 Chrysler Concorde, and 2004 Chrysler 300M. However, it is still accessible from the selected car via links, so may be relevant.

As the Oxygen Sensor signal switches, the PCM monitors the half cycle and big slope signals from the oxygen sensor. If during the 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 the monitor to pass.

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

Enabling Conditions- The following conditions must typically be met for the PCM to run the 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 (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
Closed throttle speed

Pending Conditions- The Task Manager typically does not run the Oxygen Sensor Signal Monitor if overlapping monitors are running or the 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
Intake Air Temperature
5 Volt Feed

Conflict- The Task Manager does not run the 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
Ethenal content learn is taking place and the ethenal used once flag is set

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

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