Power and Ground Signals

POWER AND GROUND SIGNALS

Vehicle Power
When the ignition switch is turned to the START or RUN position, battery positive voltage (B+) is applied to the coil of the electronic engine control (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.

Signal Return
The signal return (SIG RTN) is a dedicated ground circuit used by most electronic EC sensors and some other inputs.

Power Ground
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.