Where to take switched 12v power that doesn't cut out when cranking? (1 Viewer)

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As the title says, I need 12v that turns off when the truck is off, but stays on during cranking to run my ecu for my turbo. Anyone know where I should try? Currently I am using the BATT pin off the ecu harness but it stays powered on at all times even with the truck turned off.

Thanks!
 

Broski

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If you have removed the rear heater that may be a good source.
It’s a 20 amp Circuit.
 

alia176

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You had me at "ECU for a turbo"
 
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There should be ignition power in the ecu harness too. Use it to switch a relay for the Battery power.
 
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Interesting. I removed my rear heater. Would that be a good power source for an amplifier?
Best practices says no. 20 amps is not enough for most audio amps nor would I trust the wire size toyota used. Run new power and ground for high load accessories to prevent damage to essential wiring, and ground points. Also to mitigate potential noise introduction to the amplifier.
 
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Run new power and ground for high load accessories

I think you're best off grounding through the body and adding a heaver ground cable from the battery to the body. If you run separate grounds, it's my understanding that it leads to ground loops and subsequent electrical noise.

Maybe one of the 90s competitive car audio guys can confirm or debunk my claim.

@truthdetector aftermarket car audio amps usually get fused power directly from the battery, and only turn on when the 'remote' line from the head unit is powered. Get welding cable from your local welding supply store, and use something like a Littelfuse Mega Fuse or a Bussmann breaker at the battery.

@Pippylongsausage I run some accessories off a relay that's switched on by the GAUGE circuit, which is a yellow wire, and I just verified that it stays on during cranking. The thick black/yellow wire is IG1 and feeds GAUGE, among others. The black/white wire is 15A ECU-IG, which would probably be perfect for your needs.
 
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There should be ignition power in the ecu harness too. Use it to switch a relay for the Battery power.
I originally used the efi relay control side voltage but it cuts off when cranking. I figured that over anything else would stay energized during cranking but apparently not… problem is that the ecu shuts off and can’t start the engine.
 
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Have you tried pin 1D labeled igsw on the ecu? That feeds from the 7.5 amp ign fuse which gets power from IG2 on the ignition switch. It's how the haltech plug and play runs the 12v switch to the ecu. Also what did you end up doing to power the main relay as the ecu can only control ground sides of relays and such.
 
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I think you're best off grounding through the body and adding a heaver ground cable from the battery to the body. If you run separate grounds, it's my understanding that it leads to ground loops and subsequent electrical noise.

Maybe one of the 90s competitive car audio guys can confirm or debunk my claim.

@truthdetector aftermarket car audio amps usually get fused power directly from the battery, and only turn on when the 'remote' line from the head unit is powered. Get welding cable from your local welding supply store, and use something like a Littelfuse Mega Fuse or a Bussmann breaker at the battery.

@Pippylongsausage I run some accessories off a relay that's switched on by the GAUGE circuit, which is a yellow wire, and I just verified that it stays on during cranking. The thick black/yellow wire is IG1 and feeds GAUGE, among others. The black/white wire is 15A ECU-IG, which would probably be perfect for your needs.
You want your head unit and your amp to be at the same "ground" voltage potential. this is most easily achieved by running (oversized) grounds directly to battery. A "proper" headunit install would include running new power +ground for the headunit aswell for the amp.

Audi2nr is correct. 1D pin carries IG2 signal which will be 12v when in crank or in run.
 
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