CNG

When engine is at operating temperature, this is a Closed Loop mode. At cruising speed the Powertrain Control Module (PCM) receives inputs from:
- Air conditioning select signal, if equipped
- Air conditioning request signal, if equipped
- Battery voltage
- Engine coolant temperature sensor
- Crankshaft position 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
- Cruise control switch inputs
- 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 adjusting injector pulse width. This is done by turning the ground circuit to each individual injector on-and-off at the PCM.
- The PCM monitors O2S sensor input. It then adjusts air-fuel ratio as needed
- The PCM adjusts spark advance as necessary for rpm, temperature and load. This is done for maximum power and efficiency
- The PCM operates the air conditioning (A/C) compressor clutch through the A/C clutch relay. This is done if A/C has been selected by vehicle operator and requested by A/C thermostat
- The idle air control (IAC) motor is positioned in anticipation of the next deceleration