Firebird V8-350 5.7L VIN P SFI (1996)
Engine Control Module: Description and Operation
The Powertrain Control Module (PCM) is located in the engine compartment. The PCM is the control center of the vehicle. It controls the
following:
^
Fuel control
^
Ignition Control (IC)
^
Knock Sensor (KS) system
^
Automatic transmission shift functions
^
Manual transmission
^
Cruise Control Enable (if so equipped)
^
Generator (if so equipped)
^
Evaporative Emission (EVAP) Purge
^
A/C Clutch Control
^
Cooling Fan Control
^
Secondary Air Injection (AIR) (if so equipped)
^
Exhaust Gas Recirculation (EGR) (if so equipped)
PCM FUNCTION
The PCM supplies a buffered voltage to various sensors and switches. The PCM controls most components with electronic switches which
complete a ground circuit when turned ON.
The PCM constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The PCM also
performs the diagnostic function of the system. It can recognize operational problems. The PCM also alerts the driver through the MIL
(Malfunction Indicator Lamp). When the PCM detects a malfunction, it stores a diagnostic trouble code (DTC). A DTC stored, will identify the
problem areas. This will aid the technician in making repairs.
The PCM consists of two parts: a controller (the PCM without the Knock Sensor module) and the Knock Sensor module.
The PCM supplies either 5 or 12 volts to power various sensors or switches. This is done through resistances in the PCM. The resistance is so high
in value that a test light will not light when connected to the circuit. In some cases, even an ordinary shop voltmeter will not give an accurate
reading because its resistance is too low. Therefore, a digital voltmeter (J 39200) with at least 10 megohms input impedance is required to ensure
accurate voltage readings.
The PCM controls output circuits such as the injectors, AC, cooling fan relays, etc. by controlling the ground or power feed circuit through
transistors or a device called an Output Driver Module.
EEPROM
The Electronically Erasable Programmable Read Only Memory (EEPROM) is a permanent memory that is physically soldered within the PCM.
The EEPROM contains program and calibration information that the PCM needs to control powertrain operation.
Unlike the PROM used in past applications, the EEPROM is not replaceable. If the PCM is replaced, the new PCM will need to be programmed.
Techline equipment containing the correct program and calibration for the vehicle, is required to program the PCM.
LEGEND
(1) Powertrain Control Module (PCM)
(2) PCM Connector C3 (Gray/Clear)
(3) Knock Sensor Module Access Cover
(4) PCM Connector C4 (Blue)
(5) PCM Connector C2 (Black)
(6) PCM Connector C1 (Red)
