Deceleration

When the engine is at normal operating temperature, this is a CLOSED LOOP mode. When the engine is under hard deceleration, the controller receives the following inputs:

^ Air conditioning select signal
^ Air conditioning request signal
^ Battery voltage
^ Coolant temperature sensor
^ Crankshaft Position Sensor (CPS)
^ Manifold Air/fuel Temperature (MAT) sensor
^ Manifold Absolute Pressure (MAP) sensor
^ Neutral safety switch (Automatic Transmission)
^ Sync signal
^ Throttle Position Sensor (TPS)

If the engine controller receives a closed throttle input from the TPS and a sudden decrease in manifold pressure from the MAP sensor, it determines that hard deceleration is occurring. The engine controller will go into a fuel cut-off strategy, where it will remove the voltage from the injectors so that they cannot fire. The engine controller also ENERGIZES the EGR solenoid and the evaporative purge solenoid to prevent EGR flow and canister purge from occuring.

Based on the previous input signals, the following occurs:

^ The engine controller increases or decreases the ignition spark advance and ignition timing by applying and removing the ground path to the ignition module.
^ The engine controller will send output signals to the Automatic Idle Speed (AIS) motor, to keep the idle speed within its rpm parameter.
^ If the engine controller receives inputs that indicate that the vehicle is under deceleration (and the A/C has been selected by the driver), it will DE-ENERGIZE the A/C clutch relay (DIS-ENGAGING the A/C compressor clutch) until the vehicle is no longer decelerating.