Aug 13, 2015, 08:48 PM
Last edit by: IB Advertising
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Brake Light Problem- VERY Detailed
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Joined: Feb 2026
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This is interesting. I think the "FCU" you are talking about actually the FCM (Front Control Module). I have a very similar problem, but I just did an engine swap from 4.7 to 5.7 and haven't completed the cruise circuit yet, so I clearly have a wiring issue. This leads me to believe you also have a wiring issue, especially if it is intermittent. However, I guess it could be something with the FCM or IPM as well.
The 3rd brake light is wired straight to the switch so I agree your switch is prob fine. It might help if you can tell us what year and model truck you have.
Sorry if this isn't much help, but you might just want to hit up some junkyards and try swapping out the FCM and IPM?
The 3rd brake light is wired straight to the switch so I agree your switch is prob fine. It might help if you can tell us what year and model truck you have.
Sorry if this isn't much help, but you might just want to hit up some junkyards and try swapping out the FCM and IPM?
Last edited by aaaaaaaa; Feb 10, 2026 at 10:37 AM.