OBD System Description
OBD System Description - Catalyst MonitorSystem Description / Monitoring Procedure
Exhaust oxygen concentration at the upper part and the lower part of WU-TWC is detected from HO2S-1 and HO2S-2 respectively and accordingly ECM controls the closed loop which then controls the fuel injection volume. While the above controls is going on and if WU-TWC is in good condition, the output voltage of HO2S-2 is maintained at specified level. As WU-TWC becomes deteriorated, even when the above control is going on, the exhaust gas which has passed WU-TWC then passes HO2S-2 at the exhaust oxygen concentration similar to that of the upper part of WU-TWC without being oxygenated or converted. Thus, waveforms of HO2S- 1 and HO2S-2 output voltage become alike, ECM judges deterioration of WU-TWC by comparing waveforms of HO2S-1 and HO2S-2.
OBD System Description - Misfire Monitor
System Description / Monitoring Procedure
ECM measures the angle speed of the crankshaft based on the pulse signal from the CKP sensor and CMP sensor for each cylinder. If it detects a large change in the angle speed of the crankshaft, it concludes occurrence of a misfire. When the number of misfire is counted by the ECM beyond the DTC detecting condition, it determines the cylinder where the misfire occurred and outputs it as DTC.
OBD System Description - EVAP Control System Monitor
System Description / Monitoring Procedure
Refer to EVAP Leak Check System Description (If Equipped)
OBD System Description - Fuel System Monitor
System Description / Monitoring Procedure
As fuel system components age or otherwise change over the life of the vehicle, the adaptive fuel strategy learns deviations from stoichiometry while running in closed loop fuel. These learned corrections are stored in keep alive memory as long term fuel trim corrections. They may be stored continue to change beyond normal limits or if a malfunction occurs, the long term fuel trim values will reach a calibratable rich or lean limit where the adaptive fuel strategy is no longer allowed to compensate for additional fuel system changes. Long term fuel trim corrections at their limits, in conjunction with a calibratable deviation in short term fuel trim, indicate a rich or lean fuel system malfunction.
OBD System Description - Oxygen Sensor Monitor
System Description / Monitoring Procedure
Primary HO2S
For a primary HO2S, the system monitors maximum and minimum voltage, lean-to-rich and rich-to-lean response rates, and switching cycles. The sensor is also monitored for activity continuously.
Secondary HO2S
A secondary HO2S is used for catalyst monitoring and dual oxygen sensor control for fuel control system. During monitoring conditions, the system measures maximum and minimum output voltages and compares the voltage with malfunction criteria.
OBD System Description - HO2S Heater Monitor
System Description / Monitoring Procedure
For both primary and secondary HO2S heaters, the system monitors proper current and loaded voltage.
OBD System Description - EGR System Monitor
System Description / Monitoring Procedure
To monitor electric controlled EGR system, the system measures pressure change caused by switching of the EGR valve during deceleration condition and also measures the voltage of EGR valve stepping motor electrical circuit continuously.
OBD System Description - Thermostat Monitor
System Description / Monitoring Procedure
The engine block temperature is estimated to modelize accumulated combustion heat value since engine start (based on mass intake air flow) and radiation heat value (radiation from engine, radiation when fuel shutoff, etc.). The heat exchange value between engine and engine coolant is estimated, and the engine coolant temperature is estimated. When estimated temperature reaches the specified temperature and the measured temperature is lower than criteria, the malfunction is detected.
OBD System Description - Comprehensive Component (Engine Input) Monitor
Monitoring Procedure
Input signals of MAF (P0102 / P0103), MAP (P0107 / P0108), IAT (P0112 / P0113), ECT (P0117 / P0118), TP (P0122 / P0123), Knock sensor (P0327 / P0328) and Barometric pressure sensor (P2228 / P2229) are checked for open, short of circuit by monitoring input voltage.
OBD System Description - Comprehensive Component Rationality Monitor
Monitoring Procedure
Input signal of MAF (P0101), IAT (P0111), ECT (P0116, P0125), TP (P0121), CKP (P0335), CMP (P0340), Fuel level sensor (P0461, P0462, P0463, P0464), VSS (P0500), ECM internal circuit/memory (P0601, P0607, P0630, P1510), Starter (P0616, P0617), MAP (P1107, P1108), Barometric pressure sensor (P2227) are checked for circuit rationality by monitoring each sensor and vehicle condition.
OBD System Description - Comprehensive Component Monitor (Engine Output)
IAC System Monitor
Monitoring procedure
Input signal of Idle Air Control (IAC) is checked for open, short of circuit by monitoring input voltage.
IAC Actuator Circuit Monitor
Monitoring procedure
The Idle Air Control (IAC) solenoid functionally checked by monitoring the closed loop idle speed correction required to maintain the desired idle rpm. If the proper idle rpm cannot be maintained and the system has a high rpm (+200) or low rpm error (100) greater than the malfunction threshold, an IAC malfunction is indicated.