CNG

When engine is at operating temperature, this is a Closed Loop mode. At idle speed the Powertrain Control Module (PCM) receives inputs from:
- Air conditioning select signal, if equipped
- Air conditioning request signal, if equipped
- Battery voltage
- Crankshaft position sensor
- Engine coolant temperature sensor
- Intake manifold air temperature sensor
- CNG fuel low-pressure sensor
- CNG fuel temperature sensor
- Manifold absolute pressure (MAP) sensor
- Throttle position sensor (TPS)
- Camshaft position sensor, in distributor
- Park/Neutral Switch (gear indicator signal- auto. trans. only)
- Oxygen sensor
- Vehicle speed sensor

Based on these inputs, the following occurs:
- Voltage is applied to the fuel injectors with the PCM controlling injection sequence and injector pulse width. This is done by turning the ground circuit to each individual injector on-and-off at the PCM.
- The PCM monitors 02S sensor input and adjusts air-fuel ratio by varying the injector pulse width. It will then adjust engine idle speed through the idle air control motor
- The PCM adjusts ignition spark advance as necessary for rpm and temperature.
- The PCM operates the A/C compressor clutch through the clutch relay This is done if A/C has been selected by vehicle operator and requested by A/C thermostat