Passport LX 4WD V6-3.2L DOHC (6VD1) (2000)
/Page-594001.png)
Powertrain Control Module: Description and Operation
Circuit Operation
The engine or powertrain control module (ECM or PCM) receives inputs from the engine sensors and switches, controlling the functions of the engine. It
also turns on the malfunction indicator "check engine" light whenever a malfunction or abnormal engine performance is detected, and allows for
diagnostic testing through the data link connector (DLC).
Electrically Erasable Programmable Read Only Memory (EEPROM)
Electrically Erasable Programmable Read Only Memory (EEPROM)
The electrically erasable programmable read only memory (EEPROM) is a permanent memory chip that is physically soldered within the PCM. The
EEPROM contains the program and the 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.
Equipment containing the correct program and calibration for the vehicle is required to program the PCM.
PCM Components
PCM Components
The PCM is designed to maintain exhaust emission levels to government mandated standards while providing excellent driveability and fuel efficiency.
The PCM monitors numerous engine and vehicle functions via electronic sensors such as the throttle position (TP) sensor, heated oxygen sensor (HO2S),
and vehicle speed sensor (VSS). The PCM also controls certain engine operations through the following:
-
Fuel injector control
-
Ignition control module
-
ION sensing module
-
Automatic transmission shift functions
-
Cruise control
-
Evaporative emission (EVAP) purge
-
A/C clutch control
PCM Function
PCM Function
The PCM supplies either 5 or 12 volts to power various sensors or switches. The power is supplied through resistances in the PCM which are 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 with at least 10 megohms input impedance is required to ensure accurate voltage
readings. Tool J 39200 meets this requirement. The PCM controls output circuits such as the injectors, fan relays, etc., by controlling the ground or the
power feed circuit through transistors or through either of the following two devices:
-
Output Driver Module (0DM)
-
Quad Driver Module (QDM)
PCM Input/Outputs
PCM Input/Outputs
Inputs - Operating Conditions Read
-
Air Conditioning "ON" or "OFF"
