Monitored Circuits

The PCM contains electronic circuit monitors that monitor fuel, vehicle emissions, engine and ignition system performance. 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 and MIL will be illuminated. 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

When the MIL is illuminated, a DTC is stored. The DTC can self-erase only when MIL is out. When MIL is out, PCM must pass a diagnostic test for the most recent DTC for 40 warm-up cycles (80 warm-up cycles for fuel system monitor and misfire monitor).

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). Engine is shut off.

DTCs may be retrieved for system diagnosis. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM.