OBD-II System Readiness Tests

The catalyst efficiency monitor is a self-test strategy within the ECM that uses the downstream Heated Oxygen Sensor (HO2S) to determine when a catalyst has fallen below the minimum level of effectiveness in its ability to control exhaust emission.

Misfire is defined as the lack of proper combustion in the cylinder due to the absence of spark, poor fuel metering, or poor compression. Any combustion that does not occur within the cylinder at the proper time is also a misfire. The misfire detection monitor detects fuel, ignition or mechanically induced misfires. The intent is to protect the catalyst from permanent damage and to alert the customer of an emission failure or an inspection maintenance failure by illuminating the MIL. When a misfire is detected, special software called freeze frame data enabled. The freeze frame data captures the operational state of the vehicle when a fault is detected from misfire detection monitor strategy.

The fuel system monitor is a self-test strategy within the PCM that monitors the adaptive fuel table The fuel control system uses the adaptive fuel table to compensate for normal variability of the fuel system components caused by wear or aging. During normal vehicle operation, if the fuel system appears biased lean or rich, the adaptive value table will shift the fuel delivery calculations to remove bias.

The cooling system monitoring is a self-test strategy within the ECM that monitors ECTS (Engine Coolant Temperature Sensor) and thermostat about circuit continuity, output range, rationality faults.

OBD-II regulations require monitoring of the upstream Heated 02 Sensor (H2OS) to detect if the deterioration of the sensor has exceeded thresholds. An additional HO2S is located downstream of the Warm-Up Three Way Catalytic Converter (WU-TWC) to determine the efficiency of the catalyst.

Although the downstream H2OS is similar to the type used for fuel control, it functions differently. The downstream HO2S is monitored to determine if a voltage is generated. That voltage is compared to a calibrated acceptable range.

The EVAP monitoring is a self-test strategy within the ECM that tests the integrity of the EVAP system. The complete evaporative system detects a leak or leaks that cumulatively are greater than or equal to a leak caused by a 0.040 inch and 0.020 inch diameter orifice.

The A/C system monitoring is a self-test strategy within the ECM that monitors malfunction of all A/C system component at A/C ON.

The comprehensive components monitoring is a self-test strategy within the ECM that detects fault of any electronic powertrain components or system that provides input to the ECM and is not exclusively an input to any other OBD-II monitor.