2016 PIU brake lights stuck on

[zpbruno]

My 2016 PIU, fresh from auction, has a brake light problem. They work just fine when the ignition is turned off or the key is in accessory mode. But when the key is in the run position they are stuck on. This includes all three brake lights in the back including the high mount.

Here are things that have been tried without success, driven by lots of searching on this forum and others:
* new brake switch
* disconnect left taillight unit, disconnect right taillight unit, disconnect both taillight units
* disconnect turn signal
* The small harness immediately between the vehicle harness and the taillight assemblies has splices in the stop light circuit telling me that the previous upfit likely had something in there that they pulled when decommissioned. It appear correctly spliced.
* license plate lights not working

A shop I trust spent a fair bit of time trying to debug the problem without success. I spent quite a bit on mechanical repairs and didn't want to sign a blank check for more debugging. Their final conclusion was that something about the upfitting reprogrammed some computer configurations, and tracking that down was beyond them. This is my first foray into Fords, and I'm on the steep part of the learning curve, but perhaps I'll find something in Forscan. Any ideas welcome...

edit later that day:
problem appears to be solved by clipping out a secure-idle Inc. controller that didn't get removed in the decommissioning. Photo below.

 

[utilitytristin]

There's likely an electrical issue from the police upfitting and decommissioning of the vehicle. You can also check the upfitter harnesses behind the two cigarette lighters. Those usually have a wig wag wire and some others. They might control the brake light flashers.

 

[peterk9]

My 2016 PIU, fresh from auction, has a brake light problem. They work just fine when the ignition is turned off or the key is in accessory mode. But when the key is in the run position they are stuck on. This includes all three brake lights in the back including the high mount.

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Welcome to the Forum.

Peter

 

[zpbruno]

There's likely an electrical issue from the police upfitting and decommissioning of the vehicle. You can also check the upfitter harnesses behind the two cigarette lighters. Those usually have a wig wag wire and some others. They might control the brake light flashers.

I needed to head into that area anyway so I took a look and found a lonely aftermarket secure idle module that made it through the decommissioning. Figuring that it couldn't hurt, I clipped it out and the problem appears to be solved! Now to go back and dress some wires and replace all the trim panels I took out during debugging.