The powertrain control module (PCM) is the control
center of the engine controls system. The PCM
constantly looks at the information from various
sensors, and controls the systems that affect
emissions or engine performance. The PCM also
performs the diagnostic function of the system.
The PCM can recognize operational problems,
alert the driver through the malfunction indicator
lamp (MIL), and store a diagnostic trouble code
(DTC) or DTCs which identify the problem areas in
order to aid the technician in making repairs.

The powertrain control module (PCM) controls
most components with electronic switches which
complete a ground circuit when turned ON. These
switches are arranged in groups of 4 and 7, called
either a surface mounted quad driver module
(QDM), which can independently control up to 4
outputs, PCM terminals, or output driver modules
(ODM)s, which can independently control up to 7
outputs. Not all outputs are always used.

The control module monitors the input
components for circuit continuity and out-of-range
values. This includes performance checking.
Performance checking refers to indicating a fault
when the signal from a sensor does not seem
reasonable, for example, a throttle position (TP)
sensor that indicates high throttle position at low
engine loads or MAP voltage. The input
components may include but are not limited to the
following sensors:

•  The vehicle speed sensor (VSS)
•  The crankshaft position (CKP) sensor
•  The knock sensor (KS)
•  The throttle position (TP) sensor
•  The engine coolant temperature (ECT) sensor
•  The camshaft position (CMP) sensor
•  The manifold absolute pressure (MAP) sensor

2.2 L ( 2200 ) 4 cyl. engine data sensor

The output components respond to control module
commands. Components where functional
monitoring is not feasible will be monitored for
circuit continuity and out-of-range values if

Output components to be monitored include, but
are not limited to the following circuits:

•  The idle air control (IAC) motor
•  The control module controlled EVAP canister
purge valve
•  The electronic transmission controls
•  The A/C relay
•  The cooling fan relay
•  The VSS output
•  The MIL control
•  The cruise control inhibit
2.2L Engine Computer (PCM) Operation

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