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The ECM is "powered-up" when the ignition switch is turned ON. The heater lamp should glow for 2 seconds or so, regardless of coolant temperature. If the combination of coolant temperature and inlet air temperature is less than 770F (250C) the ECM will turn the Inlet Air Heater and lamp ON for 30 seconds as a preheat, and then go OFF. If the operator attempts to start the engine during the "preheat" cycle the ECM will take over control of the heater during the "cranking" cycle.

During the "cranking" cycle the heater will come ON if the combined temperatures of the coolant and the Inlet Air is less than 770F (250C) and will stay ON while cranking. If the engine fails to start, the heater will resume the 30 second "preheat" cycle.

After the engine has started the heater operation is still determined by the combined temperatures of the coolant and Inlet Air. The "engine started" cycle has two parts: a continuous mode, followed by an ON/OFF cycle.

The "continuous mode" lasts for a maximum of 7 minutes. The "ON/OFF" mode causes the heater to cycle ON and OFF at 10 second intervals. The "ON/OFF" mode can last up to 13 minutes.

Either of these modes can or will be interrupted when the combined temperatures of the coolant and inlet air reaches 950F (350C).

A failure or malfunction in either the inlet air sensor or the coolant temperature sensor will show up as a flash code on the "Check Engine" lamp.

Throttle/Fuel Control

The Electronic Control Module (ECM) controls the fuel flow to the cylinders. Instead of a direct rod/cable from the accelerator pedal to the fuel pump, the ECM receives a Pulse Width Modulation (PWM) from a throttle position sensor which incorporates a potentiometer. The sensor is located on the back side of the accelerator pedal.

The ECM supplies 8 volts as input voltage to the potentiometer,

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