When I have a trailer wired to my truck (2000 F250 Powerstroke, manual transmission) the engine dies when I apply the brakes. I have a Reese brake controller, and if I set the brake level to 2.5 or below, the engine runs fine. If I set it to anything else, the engine dies when the level reaches about 3.0. It doesn't matter whether the trailer brakes are activated by the vehicle braking system or by the manual switch on the brake controller.

Sometimes the MIL (Service Engine Soon light) comes on, but there is no OBDII code in the computer. Turning the iginition off/on always clears the MIL. I've also had a few engine sputters, particularly in wet weather that turn on the MIL, but there's no code then, either, and the engine runs fine after the sputter. Both problems (braking, random stalls) started around the same time.

I replaced the whole back end of the wiring harness, along with the connector sockets, as it showed some wear, but that didn't change things.

As it's a holliday weekend, I can't get a replacement controller, which is my next suspect, but in the meantime I was hoping someone had seen something similar and could help solve the mystery.

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Resolved - It looks like it was the brake controller. Likely when there was enough current going to the trailer brakes the ground was floating enough to mess up something in the engine sensors, etc. I've made several runs with the new contoller, a Tekonsha Prodigy, and there have been no more stalls on braking.

get a replacement controller

Sounds to me like that's the thing that should be replaced...despite the price of dealerships, i'd recommend taking it to the dealer if replacing the controller doesn't work.

I could be something really goofy on the internals that's doing it too.

Where does the controller get it's power from? Is it powered from an EEC fuse socket?

Also, the EEC uses the BOO (brake on off) sensor for the Torque Converter control, so if things are not wired (isolated) correctly you get feed-backs into the EEC when you shouldn't.

Intermittant stalling/hesitation is *almost* always due to a bad/failing cam (CMP) sensor.