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P0572 Brake light low...

FLHXSrider

FLHXSrider

Active Member
Contributor
Hi everybody,

I just got through dealing with a starting issue on my 2008 FLHT and now I have a new one. I'm not sure whether one caused the other or not but I won't rule it out yet. Here it goes:

When I took it for a ride, I noticed my cruise couldn't be set. A little later in the ride, my check engine light came on but the engine was working ok so I finished my ride. When I came back and checked for codes, I got P0572. This is a brake switch low error. After doing some checking around I found that it may be a problem with the rear switch. I tried disconnecting both leads on the rear switch but the light stays on. I took apart the the right handle bar switch assy to take the pressure off the front brake switch since I'd had it apart for my previous problem. It doesn't seem to matter whether the switch is pushed in or not, the light stays lit even if the rear switch is disconnected. If I hook up a meter to the rear switch leads there is about 10.7V when the front switch is activated and nothing when not. Regardless of what I try the brake is always bright like it should be.

Both brake fluid reservoirs are full. I just can't quite figure out what's happening. From what I've read, it seems like if the rear switch is disconnected, the light will go out. Not for me. Is it possible that the rear switch is stuck closed and that's causing an issue. As best I can tell all the wiring is clean and seated properly.

Does anyone have any ideas? Snow is supposed to be here tomorrow and I'm back to work (the 2 aren't related). I may not have any days left this season. As always, sorry for the long help and your help is always appreciated.

Thanks,

FLHTrider08
 
Is there not a definite way to disassembly right switch cover and pinning brake light switch so that it does not break??????
 
Front brake light switch is off when pushed in and on when released there is a heel on the brake leaver that pushes the switch in when the leaver is released
With the front brake light switch pushed in and the rear brake light switch disconnected the brake light should be off if it is still on then there may be a short circuit between the rear light circuit and the brake light circuit

Brian
 
Your brake light has a short in the wiring. There is a plug under the seat near the backrest bracket mount. Wiggle all of your wiring & connectors and see if the light goes out, then examine for worn or cut wire. If you have a Run/Stop/Turn module, check it first.

Edit; Since rereading and seeing that you've had the front switch assembly apart, that is my suspect like Fin suggested.
 
Hi Guys,

Thanks for the replies. As I mentioned "I took apart the the right handle bar switch assy to take the pressure off the front brake switch since I'd had it apart for my previous problem. It doesn't seem to matter whether the switch is pushed in or not, the light stays lit even if the rear switch is disconnected. If I hook up a meter to the rear switch leads there is about 10.7V when the front switch is activated and nothing when not."

As I can get action from the switch via voltage going on and off when the switch is activated/deactivated, I'm not sure it could be a problem with a short in the wiring but maybe I'm wrong. During all the recent repairs/checks to the handlebar switches on the right side, I was careful to put a spacer in the brake lever gap as per the Service Manual.

Unfortunately I'm working the next few days (I do 12 hour shifts) so I won't be able to look at it again for a bit. Today we got a bunch of snow but it's only supposed to be around 27F on my days off so I'm not sure if I'll ride unless the snow is gone. I'm still going to fix the problem though.

Thanks again,

FLHTrider08
 
If the brake light stays on with the rear brake light switch disconnected, that only leaves two possible causes. One is a short in the wire harness. The other is the front brake light switch. Given the information you have provided, I believe it points to a damaged wire. My guess is that you will find said wire damage inside the switch housing on the handlebar. It is very easy to pinch a wire between the two halves of the switch housing when it is reassembled. Good luck. I hate chasing down electrical gremlins.
 
The shop manual has electrical diagrams. You should be able to figure out the trigger wire for the brake light relay. Use a meter to see if that wire is hot. If it is (and you believe the front switch is good,) you have a wiring problem. If the trigger wire is dead, the relay is stuck. If the relay clicks when you put power on the bike and when power is shut off, I suspect it is working properly. By removing the wires from the rear brake switch, you have removed that part from contributing to your problem. There is a VERY SMALL chance of a double malfunction (brake light on with the rear switch out of the system) and the rear switch having failed in ON position. Either fix your problem before reconnecting the rear brake switch or check the switch for continuity with the rear brake depressed and no continuity with the pedal released. Good luck.
 
The rear brake switch is a common problem. If you have the stock switch, I would replace it anyways. Just replaced mine with a Duralast RB401 from Autozone, around 8 bucks. Mine was broken and showed different symptoms, but you never know.
 
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