3. OBD-II System Readiness Tests
The catalyst efficiency monitor is a self-test strategy within the ECM or PCM 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 is enabled. The freeze frame data captures the operational state of the vehicle when a fault is detected from misfire detection monitor strategy.
The EVAP monitoring is a self-test strategy within the ECM or PCM 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 fuel system monitor is a self-test strategy within the ECM or 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.
OBD-II regulations require monitoring of the upstream Heated O2 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.
For valve/crankcase, PCV valve is fastened to the crankcase by threaded connection to meet the requirement. Most of the case engine stalls when PCV hose is disconnected. Even the case of no stalling, there is a big engine RPM fluctuation which can easily be recognized by a driver, and the fuel trim increased up to the limit and fuel system error is detected.
The cooling system monitoring is a self-test strategy within the ECM or PCM that monitors ECTS (Engine Coolant Temperature Sensor) and thermostat about circuit continuity, output range, rationality faults.
Catalyst heating function is used to reduce cold start emission. Combination of increased engine speed and air mass flow rate (MAF) and also spark timing retardation results in faster exhaust gas temperature increase. It can be realized by opening more idle speed actuator during catalyst heating phase.
If lower air path restriction happens, engine torque is slightly decreased due to low MAF. A low MAF is compensated by spark advance increase to keep constant engine torque. But engine speed deviation does not happen in this time.
If higher air path restriction happens, even though spark timing compensates, engine speed cannot meet the target engine speed due to very low MAF.
Therefore, key control parameter for catalyst heating function is air path. Air path is represented as MAF deviation in EMS control parameter.
Continuously Variable Valve Timing (CVVT) monitoring is divided in two parts:
- Check steady deviation between camshaft set-point and actual camshaft position
- Check camshaft position response during changing camshaft set-point
The comprehensive components monitoring is a self-test strategy within the ECM or PCM that detects fault of any electronic powertrain components or system that provides input to the ECM or PCM and is not exclusively an input to any other OBD-II monitor.
The A/C system monitoring is a self-test strategy within the ECM or PCM that monitors malfunction of all A/C system components at A/C ON.
Requirement:
If a vehicle incorporates an engine control strategy that alters off idle fuel and/or spark control when the A/C system is on, the OBD II system shall monitor all electronic air conditioning system components for malfunctions that cause the system to fail to invoke the alternate control while the A/C system is on or cause the system to invoke the alternate control while the A/C system is off.
Additionally, the OBD II system shall monitor for malfunction all electronic air conditioning system components that are used as part of the diagnostic strategy for any other monitored system or component.
Implementation plan:
No engine control strategy incorporated that alters off idle fuel and/or spark control when A/C system is on. Malfunction of A/C system components is not used as a part of the diagnostic strategy for other monitored system or component.