Tracker 4WD L4-2.0L VIN C (1999)
Powertrain Control Module: Description and Operation
Powertrain Control Module (PCM) Description
General Information
Powertrain Control Module (PCM) Description
The Powertrain Control Module (PCM) is a precision unit consisting of a one chip microprocessor, an Analog/Digital (A/D) converter, and an
Input/Output (I/O) unit. The PCM is an essential part of the electronic control system. The PCM is responsible for such major functions as control of the
fuel injectors, the Idle Air Control (IAC) valve, the fuel pump relay, etc. The PCM performs the OBD 2 diagnostic tests of the emission related systems.
The PCM supplies a buffered voltage to the various information sensors and switches. The PCM controls most components with an electronic switch that
completes a ground circuit when turned on. The PCM is also responsible for a self-diagnosis function and a fail-safe function.
The PCM (1) is located below the glove box, underneath the instrument panel, on the right side of the passenger compartment.
PCM EPROM
The PCM has an Erasable Programmable Read Only Memory (EPROM) computer chip that contains the calibration information used by the PCM to
control fueling, idle speed, ignition timing, transaxle shifts and vehicle emissions. The calibration information is based on various aspects of the vehicle,
such as engine size, vehicle weight, transaxle type, final drive ratio, etc. The EPROM is programmed (flashed) with the calibration information that is
critical to proper operation of the PCM. The EPROM is soldered into the PCM and cannot be serviced separately. Replacement PCMs used for service
come with all the necessary programming already installed.
Self-Diagnosis Function
The PCM diagnoses any troubles which may occur in the engine control system when the ignition switch is in the On position with the engine running.
The PCM indicates a malfunction by illuminating the Malfunction Indicator Lamp (MIL) when a fault occurs in any of the following systems:
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Heated Oxygen Sensor 1 (HO2S 1)
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Heated Oxygen Sensor 2 (HO2S 2)
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Engine Coolant Temperature (ECT) sensor
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Throttle Position (TP) Sensor, including the CTP switch
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Mass Air Flow (MAF) sensor
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Vehicle Speed Sensor (VSS)
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Intake Air Temperature (IAT) Sensor
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Manifold Absolute Pressure (MAP) Sensor
^
Camshaft Position (CMP) Sensor
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Crankshaft Position (CKP) Sensor
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Evaporative Emission (EVAP) Control System
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Idle Air Control (IAC) System
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Misfire detection
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Fuel-trim
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Catalyst monitor
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Cooling fan control
