Code P0504, Brake Light Switch?

20064.0PCB

MEMBER
2013 FORD MUSTANG
5.0L
V8
2WD
MANUAL
10,000 MILES

Code P0504

I am looking to track down the problem.I have swapped out the 2006 Mustang 4.0 with a 2013 5.0.I have successfully installed with 2013 PCM and new wiring harness and all is working well and drives great. In the information window it will read a Engine fail safe mode when I go over 3000 RPM’s but does not affect the performance. After checking the codes found the P0504 code.I am wondering if the brake light switch for the 2006 mustang which has two terminal’s is confusing the 2013 PCM. Looking up the 2013 switch it shows four terminals. Hence my inquiry.I’m wondering if this could be a Tuner fix or is it possible to track down in the wiring diagram where the circuits perform the On and Off tasks to fix it.

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

This can be a tuner fix; they might be able to program that portion out. If not, you will need to complete the wiring for the brake light switch to the SJB (smart junction box) and the PCM. Here are the wiring diagrams so you can see how the system works and how to wire it.

The P0504 code on a 2013 Ford Mustang indicates an issue with the Brake Switch "A"/"B" Correlation.

You will need and brake light switch from the 2013 Ford Mustang. Check out the images (below). Please let us know what happens.

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