Convert to check engine light

[bronco italiano]

Wanting to convert the brake light to a check engine light. Need some assist on the wiring.
Can I connect the ground to ground and single wire on the Ron Francis EFI to the red wire?

 

[73azbronco]

what are you going to use for a brake light?

 

[bronco italiano]

what are you going to use for a brake light?

not using a brake warning light

 

[Broncobowsher]

I would swap out the bulb for LED. Less load on the computer driving the light.
Wiring is pretty simple. Computer supplies the ground, ignition supplies the power. The check engine warning light is negative switched, always has power but the computer decides if to apply ground. If you look at the original brake warning light wiring it is nearly identical. Switched ignition (or was it accessory power?) to the light and the ground was the imbalance switch.

 

[rocknhorse76]

I would swap out the bulb for LED. Less load on the computer driving the light.
Wiring is pretty simple. Computer supplies the ground, ignition supplies the power. The check engine warning light is negative switched, always has power but the computer decides if to apply ground. If you look at the original brake warning light wiring it is nearly identical. Switched ignition (or was it accessory power?) to the light and the ground was the imbalance switch.

Yeah I can’t remember on the power side either, but I just replaced the ground wire with the one from the ECU. My adjustable proportioning valve doesn’t have provisions for an imbalance switch, so it made sense to use the brake warning light as a check engine light. And yes I used an LED lamp.

 

[bronco italiano]

Thanks, I ordered LED bulbs and left a msg for RF technical dept.

 

[EFI Guy]

As said, the PCM grounds the bulb.
It's very important that power to the bulb is ignition hot only. If it is powered when the PCM is not it can damage the PCM.

This is true for any circuit that the PCM grounds.

 

[bronco italiano]

Thanks EFI guy.
-RF called me back and said to put the MIL pwr and MIL wires together to the hot lead on the bulb.
-I just suck at understanding electrical is what it really is.
Thanks and your 4G harness worked perfect!!