Cruise Or Idle Mode
When engine is at operating temperature this is a CLOSED LOOP mode. During cruising or idle, the following inputs are received by PCM:
- Manifold Absolute Pressure
- Crankshaft Position (Engine Speed)
- Inlet/Intake Air Temperature
- Engine Coolant Temperature
- Camshaft Position
- Knock Sensor
- Throttle Position
- Exhaust Gas Oxygen Content
- A/C Control Positions
- Battery Voltage
- Vehicle Speed
The PCM adjusts injector pulse width and controls injector synchronization by turning individual ground paths to injectors On and Off. The PCM adjusts engine idle speed and ignition timing. The PCM adjusts air/fuel ratio according to oxygen content in exhaust gas (measured by upstream and downstream heated oxygen sensor).
The PCM monitors for engine misfire. During active misfire and depending on severity, PCM either continuously illuminates or flashes malfunction indicator lamp (Check Engine light on instrument panel). Also, PCM stores an engine misfire DTC in memory, if 2nd trip with fault.
The PCM performs several diagnostic routines. They include:
- Oxygen sensor monitor
- Downstream heated oxygen sensor diagnostics during open loop operation (except for shorted).
- Fuel System Monitor
- EGR Monitor (If Equipped)
- Purge System Monitor
- Catalyst Efficiency Monitor
- All inputs monitored for proper voltage range, rationality.
- All monitored components (refer to Emission section for On-Board Diagnostics).
The PCM compares upstream and downstream heated oxygen sensor inputs to measure catalytic convertor efficiency. If catalyst efficiency drops below minimum acceptable percentage, PCM stores a diagnostic trouble code in memory, after 2 trips.
During certain idle conditions, PCM may enter a variable idle speed strategy. During variable idle speed strategy PCM adjusts engine speed based on following inputs.
- A/C Sense
- Battery Voltage
- Battery Temperature Or Calculated Battery Temperature
- Engine Coolant Temperature
- Engine Run Time
- Inlet/Intake Air Temperature
- Vehicle Mileage