Drive by wire relay

[JustinSinvic]

Working on swapping a Mazdaspeed 6 engine and drivetrain into another vehicle. I will be keeping the factory PCM and other components necessary to get the engine running. Looking at wiring schematics there is a relay that from what I can tell is kind of pointless, maybe its not and Im missing something. The relay is the drive by wire relay. Looking at the wiring diagram it is triggered via the PCM and sends voltage to the PCM. Overall to me just seems useless, why not just send dedicated ignition voltage to the pcm and just have the PCM internally allow the power to go where it wants. Again maybe I am just missing something. Anyone have more info on this relay?

Switch Side: Voltage from ETC Fuse through relay to PCM 4V
Coil Side: Voltage from INJ Fuse through relay to PCM 3C

 

[Raider]

@Enki, @Rokusek , thoughts?

 

[Enki]

Might have something to do with Immobilizer.

 

[Easter Bunny]

Honestly the immobiliser on these cars is so picky I wouldn't gamble on deleting anything

 

[Rokusek]

Same what what's already been stated.

If you want to delete, just go stand alone. The ECM, BCM and cluster will fight you for ever.

 

[Enki]

The problem with standalones are the injectors. They are difficult to power properly.

 

[Rokusek]

Ugg, I always forget that.

 

[Awafrican]

Motec works but man it ain't cheap

 

[Enki]

Jury is still out on whether or not you're even allowed to self tune too.

 

[JustinSinvic]

Yeah cost is main driver for not going standalone. I believe Ive worked out everything I need to do to get it running with out a bunch of extra stuff the drive by relay just puzzled me and seemed odd for the PCM to trigger a relay to just feed it self