I'm in the process of installing ACRs. The directions require attaching the wiring from the harness to two fuses in the fuse block and one to the ECM.

I'm going to hard wire it to the starter from info I've learned on the forum.

However, even though it doesn't make a difference to me since I'm not going the fuse block install route, I'm curious about why the HD wiring harness has the hot wires from the two ACRs merging into one in the harness then at the end of it separating into two which go into two fuses in the fuse block.


Any thoughts on what this is meant to accomplish?

Here's a pic of the harness with the four wires from the ACRs going in, then merging into two, and one ground and two hot coming out.

 

The short answer is that the Y/GN powers several relays. When you install the overlay ACR wiring in the fuse block the original Y/GN wire gets moved away from its power source. The extra Y/GN wire from the ACR harness is used to restores power to it.

 

Thanks! That answers the question.

 

The Y/GN wire on the Fuel Pump fuse is the power source. You move it to the spare fuse and hook one Y/GN from the ACR harness to the other side of the spare fuse to power up the ACRs. The second Y/GR acts as a jumper to hot up the fuel pump again. The V wire grounds the ACR circuit at the ECM when the ECM turns the ground on during start up. If you decide to get your current from the starter I hope your putting a inline fuse in too

 

Vernal,
thanks for taking the time to add some depth. You can count on the hot from the starter being fused! I did look over the wiring diagram and although I can follow it more or or less, there is one thing about the HD set up I still don't understand:

With the HD install method, as stated, the power comes from the fuel pump fuse and it's grounded to the ECM. So how then do the ECMs only power up with the starter switch and the current to them stops when the start up process ends? Is it the ECM ground that determines when to cut power by opening the ground? I was trying to figure out a way to use a fuse tap on the fuel pump fuse for power but seems the power would always be on.

 

The power for the fuel pump actually comes from the ECM fuse, BE/GY wire, through the NO contacts of the System Relay. When you turn your kill switch on, (Ign on) the System relay coil gets 12v on the W/BK wire and ground is controlled through the GN/O wire by the ECM. The Y/GN wire supplies power to theFuel Pump, Ignition Coil, Fuel Injectors, O2 sensors and ACRs. The ECM will ground the system relay coil for 2 seconds and if the CKP does not show the engine is rotating the ECM removes the ground and the fuel pump stops. Hit the starter and the ECM see's the CKP sows rotation and it re-grounds the system relay and power is restored to the Fuel pump.

Once the CKP shows rotation the fuel pump fuse is going to remain hot until the engine is shut down but the ECM would open the path to ground for the ACR's.

I should have mentioned earlier the Manual I've referenced is a 2010.

Clear as mud?

Good Luck
Bill

 

[QUOTE=Vernal;14958404]"The power for the fuel pump actually comes from the ECM fuse, BE/GY wire, through the NO contacts of the System Relay. When you turn your kill switch on, (Ign on) the System relay coil gets 12v on the W/BK wire and ground is controlled through the GN/O wire by the ECM. The Y/GN wire supplies power to theFuel Pump, Ignition Coil, Fuel Injectors, O2 sensors and ACRs. The ECM will ground the system relay coil for 2 seconds and if the CKP does not show the engine is rotating the ECM removes the ground and the fuel pump stops. Hit the starter and the ECM see's the CKP sows rotation and it re-grounds the system relay and power is restored to the Fuel pump.
Once the CKP shows rotation the fuel pump fuse is going to remain hot until the engine is shut down but the ECM would open the path to ground for the ACR's." END QUOTE

Vernal,
Yep- just as I suspected.

thanks for filing it out a bit.