Rear Stop Light Problem

[Warren down under]

Stop light problem

 

I noticed the intermittent activation of the following Instrument warning status lights on my 2012 Model R1200 RT:

A yellow warning triangle and a bulb with down arrow which according to my rider’s manual indicates defective rear light bulbs.

 

I check all tail lights and they were working OK. But noticed that when I applied the front or rear brakes the warning status lights would activate but the brake light failed to operate and it turned off the tail light; until the brakes were released and the tail light would turn on again.

 

The bulbs appear normal and the globe holders and contacts are clean.

 

Has anyone experienced this fault and knows how to correct it?

 

[dirtrider]

Stop light problem

 

I noticed the intermittent activation of the following Instrument warning status lights on my 2012 Model R1200 RT:

A yellow warning triangle and a bulb with down arrow which according to my rider’s manual indicates defective rear light bulbs.

 

I check all tail lights and they were working OK. But noticed that when I applied the front or rear brakes the warning status lights would activate but the brake light failed to operate and it turned off the tail light; until the brakes were released and the tail light would turn on again.

 

The bulbs appear normal and the globe holders and contacts are clean.

 

Has anyone experienced this fault and knows how to correct it?

 

Evening Warren down under

 

That is a strange occurrence.

 

The rear tail light & brake light uses the same bulbs with the ABS controller pulsing the current to the rear bulbs to lower the voltage to about 8 volts for tail light then bringing the bulbs on at full 12-14v power for brake light.

 

It sounds like-- for some reason the ABS controller is shutting the system down during brake apply. That could be due to out of spec rear bulb, or a problem the ABS controller, or something added on to the bike causing the rear brake circuit to draw too much power.

 

If you have anything connected to the rear brake light circuit (like add-on brake lights or other rear warning device) try disconnecting that.

 

If nothing connected to the rear brake wiring circuit then maybe try new bulbs (maybe one of the rear bulbs is drawing too much power)--You can also swap the turn signal bulbs into the brake light sockets for a quick test as the bulb bases & wattage are the same but the yellow bulbs will be the incorrect color to leave in place)

 

If new bulbs or disconnecting any rear add-on's doesn't cure the problem then possibly an ABS controller issue (difficult to find & pinpoint without as GS-911 & even then a GS-911 might not show a code or problem).

 

[Warren down under]

Hi Dirtrider,

Thank you for your reply.

Nothing has been added to the rear tail light circuit. The fault just appeared during a ride.

Since posting the problem I called on the Service Manager at my local BMW dealership and it also had him puzzled. He got one of the mechanics to plug the diagnostic tester into the ABS diagnostic tester plug. We changed the bulb holders and bulbs for new ones but the fault still persisted.

He suspects that there may be a short in the wiring, although none were visibly obvious.

As you say it may also be a fault with the ABS Control Unit because the brake light switches are integral to it.

I have booked the bike in for the 14th December when they will have more time to complete some further testing, unless I am able to locate the fault myself earlier.

Thanks again

 

[dirtrider]

Hi Dirtrider,

Thank you for your reply.

Nothing has been added to the rear tail light circuit. The fault just appeared during a ride.

Since posting the problem I called on the Service Manager at my local BMW dealership and it also had him puzzled. He got one of the mechanics to plug the diagnostic tester into the ABS diagnostic tester plug. We changed the bulb holders and bulbs for new ones but the fault still persisted.

He suspects that there may be a short in the wiring, although none were visibly obvious.

As you say it may also be a fault with the ABS Control Unit because the brake light switches are integral to it.

I have booked the bike in for the 14th December when they will have more time to complete some further testing, unless I am able to locate the fault myself earlier.

 

Morning Warren down under

 

It would be nice if it was just a short in the wiring but the very same wire that carries power for the tail light (& it's working) carries power for the brake light. You would think that if the wire was shorted that the tail light wouldn't work either.

 

 

You might be able to give the ABS controller a quick test by--

 

Putting bike on center stand, then turning the key on (do not start engine), then spinning the rear wheel (with your foot or with a helper), then applying the FRONT brake lever. If the rear wheel locks up then the ABS controller is at least seeing pressure input & running the rear servo.

[Guest Kakugo]

I had similar, albeit intermittant, issues.

They went away with a pair of new Osram light bulbs (much cheaper than the brand suggests ).

 

Post-mortem on one of the old bulbs revealed the base had worn off. I should still have a picture on the iPhone, I'll check later, but don't ask me how that happened.

[Warren down under]

Hi Dirt Rider,

Just back from the Bush. I will try what you have suggested in the next few days.

May I add that there was no apparent brake failure whilst I was riding.

Regards

Warren

[Warren down under]

Hi Kakugo,

Thank you for your reply.

 

I had visited my local BMW dealer and the Service Manager got the mechanic to test the lights using new bulbs holders and new bulbs but it made no difference.

 

My fault is also intermittent because when I checked the brake lights the following day they work for about 4 times then they shorted out again. However I noticed that the fault warning lights were still present during the few times the brake light operated.

 

I will check to see what brand of light bulb is fitted.

 

Regards

Warren

 

 

[Warren down under]

For those who may be interested the fault has been identified.

My local BMW dealer ran all the diagnostic checks which indicated a faulty ZFE (Central Vehicle Electronics}Unit.

Just to be sure the technician conducted a further test by borrowing a ZFE Unit from a same model R1200RT that was in for a service, and everything worked as it should.

I was quoted AU$1150 for a new ZFE unit from BMW. Mob of thieves.