Powertrain Control Hardware
Constant Control Relay Module
The constant control relay module (CCRM) interfaces with the Electronic EC system to provide vehicle power (VPWR) to the powertrain control module (PCM) and the Electronic EC system, and for the control of the cooling fan and A/C clutch. The CCRM also contains the fuel pump driver module (FPDM) power supply relay, which supplies power to the FPDM. If any of the internal components of the CCRM fail, the entire unit must be replaced. The descriptions of the specific CCRM functions, as well as the Dual Function A/C high pressure switch are found under the individual hardware - PCM inputs and outputs in this section.
Fuel Pump Driver Module
For the LS6/LS8, the FPDM functions are incorporated in the Rear Electronic Module (REM). Fuel pump operation is the same as applications using the stand-alone FPDM. The REM will, however, communicate diagnostic information through the BUS +/- circuits (SCP) instead of using a fuel pump monitor (FPM) circuit.
The fuel pump driver module (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 sends diagnostic information to the PCM on the fuel pump monitor circuit. For additional information, refer to PCM Outputs, Fuel Pump and PCM Inputs, Fuel Pump Monitor in this section.
Keep Alive Random Access Memory (RAM)
The PCM stores information in Keep Alive RAM (a memory integrated circuit chip) about vehicle operating conditions, and then uses this information to compensate for component variability. Keep Alive RAM remains powered when the ignition switch is off so that this information is not lost.
Hardware Limited Operation Strategy (HLOS)
This system of special circuitry provides minimal engine operation should the PCM (mainly the central processing unit (CPU) or EEPROM) stop functioning correctly. All modes of Self-Test are not functional at this time. Electronic hardware is in control of the system while in HLOS.
HLOS Allowable Output Functions:
- Spark output controlled directly by the CKP signal
- Fixed fuel pulse width synchronized with the CKP signal
- Fuel pump relay energized
- idle speed control output signal functional
HLOS Disabled Outputs To Default State:
- EGR solenoids
- No torque converter clutch lock-up
- Mustang - behind kick panel cover on passenger side, near instrument panel
Integrated Electronic Ignition System
The Integrated Electronic Ignition (EI) System consists of a crankshaft position (CKP) sensor, coil pack(s), connecting wiring, and PCM. The Coil On Plug (COP) Integrated EI System uses a separate coil for each spark plug and each coil is mounted directly onto the plug. The COP Integrated EI System eliminates the need for spark plug wires but does require input from the camshaft position (CMP) sensor.
Power and Ground Signals
When the ignition switch is turned to the START or RUN position, battery positive voltage (B+) is applied to the coil of the Electronic EC power relay. Since the other end of the coil is wired to ground, this energizes the coil and closes the contacts of the Electronic EC power relay. Vehicle power (VPWR) is now sent to the PCM and the Electronic EC System as VPWR.
Vehicle Reference Voltage
The vehicle reference voltage (VREF) is a positive voltage (about 5.0 volts) that is output by the PCM. This is a consistent voltage that is used by the 3-wire sensors.
Mass Air Flow Return
The mass air flow return (MAF RTN) is a dedicated analog signal return from the mass air flow (MAF) sensor. It serves as a ground offset for the analog voltage differential input by the MAF sensor to the PCM.
The signal return (SIG RTN) is a dedicated ground circuit used by most Electronic EC sensors and some other inputs.
Power ground (PWR GND) is an electric current path return for VPWR voltage circuit. The purpose of the PWR GND is to maintain sufficient voltage at the PCM.
Gold Plated Pins
NOTE: Damaged gold terminals should only be replaced with new gold terminals.
Some engine control hardware has gold plated pins on the connectors and mating harness connectors to improve electrical stability for low current draw circuits and to enhance corrosion resistance. The electronic EC components equipped with gold terminals will vary by vehicle application.