Powertrain Control Hardware
POWERTRAIN CONTROL HARDWAREPowertrain Control Module (PCM)
The center of the engine control (EC) system is a microprocessor called the PCM. The PCM receives input from sensors and other electronic components (switches, relays). Based on the information received and programmed into its memory, the PCM generates output signals to control various relays, solenoids and actuators. There are several different types of PCMs in use for this model year. Refer to the Vehicle PCM Application Table below for PCM types and their applications.
PCM Locations
For PCM locations, removal and installation procedures, refer to the Computers and Control Systems, Electronic Engine Controls.
Fuel Pump Control Module
Note: The Mustang 5.4L uses 2 fuel pump control modules to control fuel for the fuel delivery system. The PCM outputs only one fuel pump duty cycle on the fuel pump control (FPC) circuit. Both fuel pump control modules use this circuit. The PCM individually monitors the fuel pump control modules through the FPM and FPM2 circuits. The fuel pump control module located on the driver side of the luggage compartment is referred to as Fuel Pump Control Module 1 and the fuel pump control module located on the passenger side of the luggage compartment is referred to as Fuel Pump Control Module 2.
The fuel pump control module receives a duty cycle signal from the PCM and controls the fuel pump operation in relation to this duty cycle. The PCM requests low or high speed fuel pump operation depending on engine fuel demand. The fuel pump control module controls the fuel pump by switching the fuel pump power circuit ON and OFF at the required duty cycle. The fuel pump control module sends diagnostic information to the PCM on the fuel pump monitor (FPM) circuit. For additional information on the fuel pump control and the fuel pump monitor, refer to Fuel Systems.
On vehicles with gasoline direct fuel injection, the high pressure fuel system may be under vacuum after several hours of cold soak. Fuel vapor may collect at the fuel injection pump, causing a long start condition. To prevent this, the fuel pump relay is energized for 1 or 2 seconds, depending on application, as soon as the dome light is commanded ON. This causes the fuel pump control module and the fuel pump to cycle for 1 or 2 seconds and purge any trapped air or fuel vapor from the high pressure fuel system.
Fuel Pump Driver Module (FPDM)
The FPDM receives a duty cycle signal from the PCM and controls the fuel pump operation in relation to this duty cycle. This results in variable speed fuel pump operation. The FPDM controls the fuel pump by switching the fuel pump return circuit ON and OFF at the required duty cycle. The FPDM sends diagnostic information to the PCM on the FPM circuit. For additional information on the fuel pump control and the fuel pump monitor, refer to Fuel Systems.
Keep Alive Memory (KAM)
The PCM stores information about vehicle operating conditions in the KAM (a memory integrated circuit chip) and then uses this information to compensate for component variability. The KAM remains powered when the ignition is in the OFF position so the information is not lost.
Power and Ground Signals
Accelerator Pedal Position Reference Voltage (APPVREF)
APPVREF is a consistent positive voltage (5 volts plus or minus 0.5 volt) circuit.
Accelerator Pedal Position Return (APPRTN)
APPRTN is a return path for APPVREF circuit.
Electronic Throttle Control Reference Voltage (ETCREF)
ETCREF is a consistent positive voltage (5 volts plus or minus 0.5 volt) circuit.
Electronic Throttle Control Return (ETCRTN)
ETCRTN is a return path for ETCREF circuit.
Gold Plated Pins
Note: Gold plated terminals should only be replaced with new gold plated terminals.
Some engine control hardware has gold plated pins within the connectors and mating harness connectors to improve electrical stability for low current draw circuits and to enhance corrosion resistance. The engine control (EC) components equipped with gold terminals vary by vehicle application.
Keep Alive Power (KAPWR)
KAPWR provides a constant voltage input independent of ignition switch state to the PCM. This voltage is used by the PCM to maintain the KAM.
Mass Airflow Return (MAFRTN)
The MAFRTN is a signal return circuit from the MAF sensor.
Power Ground (PWRGND)
The PWRGND circuit(s) provides a return path for the PCM vehicle power (VPWR) circuits.
Signal Return (SIGRTN)
SIGRTN is a dedicated return path for VREF applied components.
Starter Motor Request (SMR) Circuit
The SMR circuit provides the PCM with a signal from the ignition switch to the PCM. The input is pulled high when the ignition is in the START position and the transmission range (TR) sensor ignition lockout circuit allows the starter to engage.
Variable Reluctance Sensor Return (VRSRTN)
The VRSRTN circuit is a dedicated return path for variable reluctance (VR) type sensors.
Vehicle Buffered Power (VBPWR)
VBPWR is a regulated voltage supplied by the PCM to vehicle sensors. These sensors require a constant 12 volts for operation and cannot withstand VPWR voltage variations. VBPWR is regulated to VPWR minus 1.5 volts and is also current limited to protect the sensors.
Vehicle Power (VPWR)
VPWR is the primary source of PCM power. VPWR is switched through the PCM power relay.
Vehicle Reference Voltage (VREF)
VREF is a consistent positive voltage (5 volts plus or minus 0.5 volt) provided by the PCM. VREF is typically used by 3-wire sensors and some digital input signals.