NPR L4-5.2L DSL Turbo (2005)
Engine Control Module: Description and Operation
Description and Operation
Engine Control Module (ECM) Description
The engine control module (ECM) is located on the chassis frame side near the transmission. The ECM controls the following:
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The fuel supply control
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The fuel injection timing control
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The exhaust gas recirculation (EGR) control
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The preheating control (glow control)
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The on-board diagnostics for engine control
The ECM constantly observes the information from various sensors. The ECM controls the systems that affect vehicle performance. The ECM performs
the diagnostic function of the system. The ECM can recognize operational problems, alert the driver through the malfunction indicator lamp (MIL), and
store diagnostic trouble codes (DTCs). DTCs identify the system faults to aid the technician in making repairs.
ECM Function
The ECM supplies 5-12 volts to power various sensors or switches. In some cases, the power is supplied through resistances in the ECM are high enough
in value that a test lamp will not illuminate when connected to the circuit. In some cases, even an ordinary shop voltmeter will not give an accurate
reading because the voltmeter resistance is too low. Therefore, a DMM with at least 10 Mohm input impedance is required to ensure accurate voltage
readings.
Malfunction Indicator Lamp (MIL) Operation
The malfunction indicator lamp (MIL) is located in the instrument panel cluster. The MIL will display the following symbol when commanded ON:
The MIL indicates that an emission related fault has occurred and vehicle service is required. The following is a list of the modes of operation for the
MIL:
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The MIL illuminates when the ignition switch is turned ON, with the engine OFF. This is a bulb test to ensure the MIL is able to illuminate.
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The MIL turns OFF after the engine is started if a diagnostic fault is not present.
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The MIL remains illuminated after the engine is started if the engine control module (ECM) detects a fault. A diagnostic trouble code (DTC) is
stored any time the ECM illuminates the MIL due to an emission related fault.
ECM Voltage Description
