Fuel Control

FUEL CONTROL
The PCM controls fuel by receiving input signals from various sensors. It then takes this information and calculates the amount of fuel required to achieve a specific air/fuel ratio. The PCM controls the fuel flow into the engine by controlling four fuel injectors. This is multi-port fuel injection (MFI) system. The PCM pulses the injectors at least once every crankshaft revolution.

Fuel Backup Control
If the PCM should become non-operational, the PCM will deliver a set amount of fuel, based on inputs received from the manifold absolute pressure (MAP) sensor and engine coolant temperature (ECT) sensor.

Spark Timing Control
The PCM receives references signals from an electronic ignition module so that it can calculate the spark output signal. The spark output signal controls the timing of the primary of the ignition coils. The PCM also provides spark retard when knock conditions are detected by a knock sensor mounted in the engine block.

Engine Cooling Fan Control
The PCM controls operation of the engine cooling fan based on coolant temperature, air conditioning state and vehicle speed. If the coolant rises above 105°C (220°F) or if the air conditioning compressor is turned On, the PCM will supply a ground to the engine coolant fan relay, energizing the relay and engine cooling fan. The PCM will shut-off the cooling fan under the following conditions:
1. Vehicle exceeds 97 km/h (70 mph) for three minutes.
2. When the PCM stops receiving an A/C request signal, it will run the cooling fan for three minutes, then de-energize the relay turning off the cooling fan. The A/C request signal can be removed by the operator turning the A/C switch to Off; or by the A/C high or low pressure switches opening the A/C request circuit from the A/C control head to the PCM.

If the PCM is non-operational, the cooling fan will be turned On, as long as the engine is moving.
The cooling fan is turned On, after a initialization delay, when any of the following conditions are present:
1. A coolant temperature sensor failure has been detected (Codes 14, 15, 17 - Flags 73 or 74).
2. When coolant temperature exceeds 105.5°C.
3. Vehicle is turned OFF and Engine Coolant temperature is 110°C or greater.