Brake Activates Ignition

[TerryD40]

Hi everyone!

I have a 2009 D40 STX turbo diesel.

I have a truly weird problem that I can't seem to resolve. When I press the brake pedal, my ignition comes on, even with the key in my pocket! If my engine is already running, it keeps going until I remove my foot from the brake. If the engine is NOT running, it won't start, but all the dash lights up (except where the clock/4WD/temperature is displayed), even the fuel gauge comes on.

Here's what I've tried.

* Removed the turbo timer.
* Replaced the airbag module (I did have a flashing airbag light)
* Disconnected all of the tail lights from the main plug under the back
* Checked fuses and relays under the bonnet in all 3 locations
* Examined wiring looms for damage (haven't been able to see any problems)
* Removed the plug from the lower brake switch - problem goes away

In all but the last case the problem persists. I've cleaned that switch, I've checked it carefully and it looks fine.

Has anyone seen this sort of thing before?

 

[Tms40]

Best I’ve got

 

[trgraceing]

Hi everyone!

I have a 2009 D40 STX turbo diesel.

I have a truly weird problem that I can't seem to resolve. When I press the brake pedal, my ignition comes on, even with the key in my pocket! If my engine is already running, it keeps going until I remove my foot from the brake. If the engine is NOT running, it won't start, but all the dash lights up (except where the clock/4WD/temperature is displayed), even the fuel gauge comes on.

Here's what I've tried.

* Removed the turbo timer.
* Replaced the airbag module (I did have a flashing airbag light)
* Disconnected all of the tail lights from the main plug under the back
* Checked fuses and relays under the bonnet in all 3 locations
* Examined wiring looms for damage (haven't been able to see any problems)
* Removed the plug from the lower brake switch - problem goes away

In all but the last case the problem persists. I've cleaned that switch, I've checked it carefully and it looks fine.

Has anyone seen this sort of thing before?

hi has this got trailer brake controller fitted if so disconnect and try it

 

[Tms40]

Geez I forgot about suggesting that. My brake controller sporadically put my car into limp mode. You couldn’t pick the day or time. Was just random.

 

[TerryD40]

Thanks for the replies. Yes it has a brake controller for a trailer and I've tried unplugging it - it didn't resolve the problem. I'll now try and remove all the associated wiring and see if that fixes it.

 

[landmannnn]

And check the trailer socket.

 

[wechosethegoodlife]

And check the trailer socket.

Possibly the +12v charging circuit for the breakaway brakes is from an ignition feed & somehow (probably trailer socket) there's are short between brake wire & that said +12v feed.

 

[TerryD40]

I've taken the trailer socket apart and cleaned it, checking each wire for damage and frayed strands that might connect to another wire. There's no crush damage, there was only a small amount of dirt inside which I've cleaned up. Problem persists.

I haven't dismantled the wiring at the front yet, I'm starting to suspect the problem is in there somewhere.

 

[Old.Tony]

Try removing and replacing the brake switch attached to the pedal. In the auto, it's the lower one. You could try cleaning it and checking the contacts are making the right connections. It's a simple twist-out to remove it.