Powertrain Control Software

Description and Operation 1-51

Powertrain Control Software

Powertrain Control Software

Adaptive Airflow

Some vehicles equipped with electronic throttle control (ETC) have an adaptive airflow strategy that allows the PCM to correct for changes in the airflow. During idle, the PCM monitors the throttle angle and airflow. If the airflow is determined to be less than expected, the PCM adjusts the throttle angle to compensate.

The PCM only learns the adaptive airflow when the vehicle is at idle and normal operating temperature and the airflow is less than a calibrated limit. Whenever the battery is disconnected or the keep alive memory (KAM) is reset, it is necessary for the PCM to learn the new value and not use the default value. For additional information on a KAM reset, refer to Section 2, Resetting The Keep Alive Memory (KAM).

Auto Start Stop

The auto start stop system helps reduce fuel consumption and decrease emissions by automatically shutting down the engine when the vehicle stops and the engine is idling, usually within 1500 ms (1.5 seconds). To initiate the auto start stop operation, the vehicle gear selector must be in DRIVE when the vehicle comes to a stop and the brake pedal must be fully applied. The engine automatically restarts when the brake pedal is released, usually within 200 ms (0.5 seconds), or when a vehicle system requires a restart, for example to recharge the battery or to maintain interior comfort settings.

The auto start stop system is defaulted to an ON state when the engine is started. To switch the auto start stop system OFF, press the auto start stop switch located on the center console. To turn the auto start stop system ON, press the auto start stop switch again. The auto start stop system can only be deactivated during the current ignition cycle.

The instrument panel cluster (IPC) auto start stop indicator illuminates when an auto start stop system inhibit or disable condition is present.

During normal operation the auto start stop system may not stop the engine under the following conditions:

• The A/C, heat or defrost settings are ON

• The rear defroster is ON

• The battery has a low state of charge or is below 5°C (41°F) or above 60°C (140°F)

• The maximum engine off time is exceeded

• The engine operating temperature is less than 60°C (140°F)

• The gear selector is in the PARK, REVERSE, NEUTRAL or SECOND GEAR position

• The steering wheel is turned rapidly or is at a sharp angle

• Initial vehicle speed of greater than 4 km/h (2.5 MPH) and less than 2 seconds has elapsed

• The vehicle is on a steep road grade

• Elevation is above 10,000 feet (3,048 meters) approximately

• The clutch pedal position (CPP) sensor indicates the clutch pedal is fully released

Any of the following conditions may result in an automatic restart of the engine:

• The blower fan speed is increased or the climate control temperature is changed

• An electrical accessory is turned ON or plugged in

• Incorrect brake vacuum

• The auto start stop switch is pressed to disable the system while the engine is stopped

Automatic Engine Idle Shutdown

Vehicles equipped with automatic engine idle shutdown have an instrument panel cluster message and an audible alert that notifies the driver 30 seconds prior to engine shutdown. When the shutdown occurs, the PCM broadcasts a shutdown message and vehicle power is disabled.

Shutdown occurs under the following conditions:

• The vehicle is stationary

• The gear selector is in the PARK or NEUTRAL position or the clutch pedal is released

• The accelerator pedal is released

• The brake pedal is released

• Scan tool is not connected

2016 Powertrain Control/Emissions Diagnosis, Gasoline Engines, 3/2015