Other Control Functions

A/C COMPRESSOR CLUTCH RELAY
When the Engine Control Module (ECM) receives a demand for cooling from the air conditioning system (compressor control unit), it delays the compressor from being energized, and enriches the mixture to assure smooth transition to the A/C mode.

EVAPORATIVE EMISSION (EVAP) PURGE CONTROL SOLENOID VALVE
When the engine coolant temperature is below 75°C (167°F) and air conditioner OFF the ECM supplies a ground to the EVAP purge control solenoid valve which cuts vacuum to the EVAP purge control diaphragm valve.

EXHAUST GAS RECIRCULATION (EGR) CONTROL SOLENOID VALVE
When the EGR is required for control of oxides of nitrogen (NOx) emissions, the ECM supplies ground to the EGR control solenoid valve which supplies regulated vacuum to the EGR valve.