Vibe FWD L4-1.8L VIN 8 (2004)
Engine Control Module: Description and Operation
POWERTRAIN CONTROL MODULE (PCM) DESCRIPTION
The powertrain control module (PCM) is a precision 32-bit microprocessor and is an essential part of the electronic control system. The PCM (1) is
located below the instrument panel (IP) storage compartment. Communication with the PCM is through the data link connector (2) located on the left
side below the IP. The PCM performs the OBD II diagnostic tests of the emission related systems. The PCM supplies a buffered voltage, called
reference 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 electronic switch is commonly referred to as an output driver. The PCM is also responsible for a self-diagnosis
function and a fail-safe function.
Self-Diagnosis Function
The powertrain control module (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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The heated oxygen sensor 1 (HO2S 1)
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The heated oxygen sensor 2 (HO2S 2)
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The engine coolant temperature (ECT) sensor
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The throttle position (TP) sensor (including the CTP switch)
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The vehicle speed sensor (VSS)
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The intake air temperature (IAT) sensor
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The mass air flow (MAF) sensor
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The camshaft position (CMP) sensor
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The crankshaft position (CKP) sensor
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The knock sensor (KS) system
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The evaporative emission (EVAP) control system
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The idle air control (IAC) system
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The CMP actuator solenoid system
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The rocker arm oil control system
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The misfire detection
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The fuel-trim
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The catalyst monitor
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The central processing unit (CPU) of the PCM
When the PCM detects a malfunction in one of the above areas, the PCM will illuminate or flash the MIL in order to notify the driver of the
occurrence of a fault.
Malfunction Indicator Lamp (MIL) Operation
