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Discussion Starter · #1 ·
I'm asking the question on this forum because it's not really specific to the GS/GSA. It's an electronics problem that I'm hoping a BMW canbus guru can provide some help in diagnosing.
This is my 'second' bike that doesn't get a lot of use. In fact I was prepping it for an inspection when I first noticed the problem.
2015 R9T with LED tail and brake light.
Pull front brake lever, brake light works fine.
Press rear brake pedal, nothing.
My circuit diagram shows the switch to be 'normally closed' so logic dictates that if the switch is stuck, disconnecting it would simulate it opening and operate the brake light. Tried this, didn't activate brake light.
Plugged in my motoscan, got the following data.
Central Chassis Electronics, fault codes - none.
Live data, Front brake light switch voltage at rest 2.48V, lever pulled 2.48V, brake light activates.
Live data, Back brake light switch voltage at rest 6.6V, depressed pedal, voltage drops to 2.48V, no brake light.
One final thing I did was disconnect the back brake switch again and the 'at rest' voltage dropped to 2.48V.
So I'm of the opinion that the switch is functioning perfectly, as is the LED light.
Why am I getting a higher voltage across the rear brake light switch which I assume is the signal voltage for the ECU.
I'm seriously baffled so any help would be appreciated.
 
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