Cruise or Idle Mode

Fig. 26 Throttle Body:

When the engine is at normal operating temperature, this is a closed loop mode.

During cruising or idle the following inputs are received by the PCM:
- Intake air temperature
- Engine coolant temperature
- Manifold Absolute Pressure (MAP)
- Crankshaft position (engine speed)
- Camshaft position
- Knock sensor
- Throttle position
- Exhaust gas oxygen content
- A/C control positions
- Power steering pressure switch
- Battery voltage
- Vehicle speed

The PCM adjusts injector pulse width and controls injector synchronization by turning the individual ground paths to the injectors On and Off.

The PCM adjusts engine idle speed and ignition timing.

The PCM adjusts the air/fuel ratio according to the oxygen content in the exhaust gas (measured by the upstream heated oxygen sensor).

The PCM monitors for engine misfire. During active misfire and depending on the severity, the PCM either continuously illuminates or flashes the malfunction indicator lamp (Check Engine light on instrument panel). Also, the PCM stores an engine misfire DTC in memory

The PCM performs several diagnostic routines:
- Oxygen sensor monitor
- Fuel system monitor
- EGR monitor
- Purge system monitor
- All inputs monitored for proper voltage range.
- All monitored components (see On-Board Diagnostics).

During certain idle conditions, the PCM may enter a variable idle speed strategy. During variable idle speed strategy the PCM adjusts engine speed based on the following inputs:
- A/C sense
- Battery voltage
- Battery temperature
- Engine coolant temperature
- Engine run time
- Vehicle mileage