Gen 3 Coyote MIL question

[Cincy123]

Since my first start I’ve noticed my MIL comes on when key is turned to on and stays on after the start. The light is very very dim and stays on for a short time after the key is turned to off. When I disconnect the light and wire it directly to a 12 v source it is bright as one would expect. I tapped into the port with my scanner and no codes are shown and it shows the mIL as being off in the printable display. Not sure what to make of this and any trouble shooting suggestions are welcome!

[Lidodrip]

That is normal (being dimly lit when running, no codes). When it comes on because of a code, it will be bright like when you tested it with a 12v source. Threw me for a loop the first time I saw it, but fortunately this behavior was well explained on this forum. It doesn't matter if you use the Ford supplied MIL or replace it with a third party MIL - it will still be dimly lit when running/no codes.

James

[edwardb]

As James said, normal behavior. (In spite of what the Ford Performance instructions say.) That delay you see when shutting down is also by design. Typically you'll hear relays in the PDB clicking when the light goes out. In an open top Roadster, the dim light isn't typically visible except at night. For the Coupe, you can see it glow all the time. I consider it my "system is alive" indicator. Back when this subject first came up (the Gen 2 did the same thing) I played around with a variety of resistors to change the forward voltage and turn off the dim and only light when the MIL was signaled. Lots of internet posts about such things with LED's. I was never able to come up with a satisfactory solution. It's a ground switching circuit, and even when not signaled, there's low voltage on the line from the PCM. So changing lights doesn't fix it either. I live with it and it's no big deal.

[Cincy123]

Thanks everyone, I’m glad there is nothing to be concerned about here.