Acc 12v pwr supplied to mfi relay?

[Blitz_86]

Does the Ecu provide the 12v to the mfi relay to kick on power to pin 38? I'm havin weird problem I'm only gettin .75v at the power for all my 12v sensors under the hood, maf cas fuel inj resistor plug o2 plug. I'm stumped

 

[steve]

The ECU doesn't provide power (voltage) to the MPI relay. It completes the circuit for the MPI relay coil by switching one side to the ground causing current to flow.

On a 2G Turbo (with a single MPI relay) ECU pin 38 (blue/green) is the one that pulls MPI relay coil pin 6 to ground. The other side of that coil is pin 8 (red/black) which is connected to the 20A fusible link #4 for the MFI system. When ECU pin 38 is floating the voltage on the pin should be battery voltage and the relay off. When the pin is pulled low, the voltage should be close to 0 volts, current should be slowing in the relay coil and the relay active causing battery voltage to be switched from MPI Relay pin 4 to MPI relay pin 2 and 3 (red). Pin 2 goes the bulk of the engine sensors and solenoids and pin 3 to the MAF and ECU.

The ECU gets power to do this from the backup power connection on pin 80 (red/blue) which comes from dedicated fuse #11 which in turns comes from Fusible Link #2.