Wiring up kill switch, duramax

[Smokemebroke]

Wonder how people are wiring up there kill switch on a duramax. I don't want to ground out the wire so it blows the fuse, or use an extension cord. Any help would be appreciated.

[Chris611]

Splice into the ECM power with a relay. The ECN power goes between terminals 30 and 87 of the relay. (This is the NO terminal). Run +12V to terminal 85 and then a ground from terminal 86 to the back of the truck to the plug (I used a trailer disconnect plug), then from the plug to ground (Frame). When you key the truck on, the relay closes and provides power the the ECM, when the plug is pulled, the signal to relay is disrupted and the relays switches back and disconnects power to the ECM. No blown fuses. If the plug gets pulled, just put it back in and your ready to go.

[Smokemebroke]

Thank you very much. Wanted to make it look clean without blowing a fuse. Just use a regular 4 post relay?

[lawnboy01]

Originally Posted by Smokemebroke

Thank you very much. Wanted to make it look clean without blowing a fuse. Just use a regular 4 post relay?

Yes

[Chris611]

It's just a regular 12 volt relay but it will have 5 posts. 85 + 86 is the signal to trigger the relay. So 12 volt Supply across these two causes the relay to switch. Terminal 30 is where you supply the power for the ECM. Post 87a is the normally closed post. This is the post that is connected to number 30 when the signal is not powered. When you apply power across 85 and 86 the relay switches from 87a to 87. 87 is where you will hook the ECM.

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[20dirtymax03]

So is this done before or after the fuse? And just so I this right.

cut wire for ecm connect one end to the 30 and the other to 87 posts so it loops

supply 12v+ to post 85

connect wire from trailer disconnect plug to post 86

connect other wire from trailer disconnect to frame (ground)

so would post 87A have 12V+ to it when trailer plug is disconnected?

Or do I have this wrong??
thanks kyle

[duramaxsandwich]

When I first started I killed power to the ecm but had one time I was logging the run and kill switch got pulled ecm lost power and went back to recover the data log and it was gone. We found it better just to kill power to the FICM on my truck then it still has the data log intact. And that's also how we shut the truck off too. Forgot a couple times and shut the truck off when the truck broke and lost all the data there too.

[IdahoRob]

I just kill the power to the ecm with the kill switch, I've never lost data but haven't tried it on an 01. Remember to run the alternator feed wire to the other side of the kill switch or it will continue to power up the ecm (truck will not shut off) even when the switch is thrown.

[Chris611]

I think I have a mistake in my original post with regards to the 87 post. I will try and correct this. You have the 85 & 86 post hooked up correctly. So you will provide 12v to post 30 on the relay. This is what will power the ECM. As the relay sits with no signal voltage applied (power & ground @ posts 85&86) the power applied at 30 will be connected to 87a. Wire the power wire of the ECM to 87a. This allows power to the ECM as long as there no signal voltage/ground to 85/86.

Theory: when the trailer plug get pulled out, it completes the circuit for the signal at pins 85&86. This causes the relay contacts to switch from 30-87a to 30-87. Since the ECM power is hooked to 87a, power is removed from the ECM. At that point there will be power to pin 87; however there will be no wire hooked up to 87. Just make sure the 87 pin can't accidentally touch ground! when you plug the trailer disconnect back in, you break the circuit to the signal and the relay switches back to 30-87a and the ECM has power again.

Hope this helps.

[20dirtymax03]

Thanks chris611. It makes a lot more sense now!