On-Board Diagnostics

The Powertrain Control Module (PCM) monitors several different engine control system circuits. If malfunction occurs, PCM may store a Diagnostic Trouble Code (DTC) when malfunction is detected, and PCM will enter limp-in mode. In limp-in mode, PCM substitutes values for failed component and provides continuous engine operation.

The PCM contains electronic circuit monitors that monitor fuel, vehicle emissions, engine and ignition system performance. Monitors use information from various sensor circuits for system monitoring. Monitors do not indicate a specific component failure, but do indicate an implied failure within a specified system, and that the problem must be diagnosed. If any monitor detects a problem affecting vehicle emissions, a Diagnostic Trouble Code (DTC) will be stored in PCM. The following monitors are used.

EGR Monitor
Engine Misfire Monitor
Fuel System Monitor
Oxygen Sensor Monitor
Oxygen Sensor Heater Monitor
Catalyst Monitor
EVAP System Leak Detection Monitor

The PCM will erase DTC once MIL is turned off. Once MIL is turned off, PCM must not detect the recent malfunction during 40 warm-up cycles on normal operation, or 80 warm-up cycles on engine misfire or fuel system monitor.

NOTE: A warm-up cycle is defined as the engine is started, an increase of 40°F (4°C) in engine coolant temperature exists after engine is started and engine coolant temperature reaches at least 160°F (71°C).

DTCs may be retrieved for system diagnosis. SeeRETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. System malfunctions are identified as either hard failures or intermittent failures.