2007 AE No brake lights

[jtnwevo]

Hi guys,

I have a 2007 AE with about 65,000 miles that I have owned since new. Just found out my brake lights are not working. No idea how long they have been out. I do have a Backoff module but removed it for troubleshooting.

I have discovered that there is +8V being supplied to the yellow brake wire even when the 15amp "Signal" fuse is pulled. Neither brake lever changes the voltage reading and I can hear the brake light relay clicking with either the hand or foot brake applied.

If I pull the 10amp "ABS Control" fuse this voltage goes away but I still dont have brake lights.

I disconnected the tail light connector under the left side cover to check the voltage on the yellow wire so can confirm it is coming from the big harness side. If I apply +12V to the other end of the yellow wire the brake lights light up as they should. All other lights are working normally.

Any one have any insights or thoughts on this? Is my ABS computer dead?

 

[jtnwevo]

Hey guys, I just jumpered the ABS test connector in front of the battery and got codes 11, 24, and 25.

11- Front wheel sensor signal is not received properly

24 - Brake light is defective

25 - No signal is received from the front wheel sensor when the vehicle starts moving.

I did notice lately that the ABS light would start to blink sometimes after leaving a stop. When it first started happening I removed, clean, and reinstalled both wheel speed sensors.

The FSM suggests the brake light relay may be a cause and I have located it but cant seem to remove it due to limited access in the front fairing. Any one have any tips? Do I have to remove more of the fairing?

Thanks

JT

 

[RossKean]

Are you certain that the brake light is not on? Is it possibly on all the time? A sticking rear brake pivot (common) can cause the ABS light you mentioned and could explain why there is no apparent light. Just something to check.

 

[jtnwevo]

Hi Ross, if the brake lights were stuck on they would have been flashing due to my Backoff brake light modulator. I have removed it for now and verified that it works. I've been aware of the stuck pivot issue and keep it lubed.

Also, I have unplugged both brake switches and jumpered both connectors. I get the +8V at the yellow brake light wire regardless of the brake switch jumpers being in place or not.

Unless I am mistaken there should be 0V at the yellow wire until I use one of the brakes then it should have +12V and return to 0 when I let go.

Thanks!

 

[jtnwevo]

I managed to pull the brake light relay and it passes the tests in the FSM but doesn't seem quite right so I am going to replace it. It's less than $25 so might as well. I recently had to replace the starter relay it passed the tests in the FSM too but was not working. Hopefully that is the same situation here.

Still open to any other suggestions from folks. Will update this weekend after the new relay arrives.

Thanks again.

JT

 

[JamesK]

Hi Ross, if the brake lights were stuck on they would have been flashing due to my Backoff brake light modulator. I have removed it for now and verified that it works. I've been aware of the stuck pivot issue and keep it lubed.
Also, I have unplugged both brake switches and jumpered both connectors. I get the +8V at the yellow brake light wire regardless of the brake switch jumpers being in place or not.

Unless I am mistaken there should be 0V at the yellow wire until I use one of the brakes then it should have +12V and return to 0 when I let go.

Thanks!

Just a thought, but sounds like you have a bad earth somewhere in that circuit.

 

[mcatrophy]

The 8V is there from the ABS computer so that it can check that the brake circuit exists. The 8V should be pulled to near zero by the bulbs' filaments.

As yours isn't pulled to zero, you must have a connection problem, probably in the connector to the rear lights.

(You've eliminated bulb failure which would also cause this residual voltage.)

Edit - Just noticed yours is the AE. The gear-shift computer (MCU) also puts a voltage on the brake light wire for a similar reason (albeit through a diode).

Edit 2 - Found a diagram I did some time ago that may help.

 

[SunRider]

While I agree with the 'Note' about the switches & Brake Light relay,

perhaps it should be noted the relay is shown without ignition power applied.

Interesting about this circuit, the ABS ECU can tell which brake

Lever/Pedal is applied because of the voltage presented on the brown/black wire.

Batt -> Rear only

Gnd -> Front only

Bias -> Both applied, where the Bias is set within the ECU.

This is great use of a single ECU input.

 

[mcatrophy]

While I agree with the 'Note' about the switches & Brake Light relay,perhaps it should be noted the relay is shown without ignition power applied.

...

It's normal to refer to "normally" as being in the unpowered or unactivated state in the electronics world.

Where there might be some sort of issue is that the front brake switch is in reality a "normally open" switch, but mounted in such a way that it is held in its "closed" state when the brake lever is in its relaxed state. When the brake lever is pulled back, the switch relaxes. But my diagram shows it with the lever relaxed, and that's what my note refers to.

But I didn't want to complicate the issue in what is a fairly tricky circuit for the simple task of switching the brake lights.

 

[jtnwevo]

Thanks for the input guys, I'm glad to hear the +8V is supposed to be there. My new brake light relay is supposed to be here Friday and hopefully it is the root of my issues. Will update thread then.

Thanks again!

 

[wfooshee]

Um.... are the bulbs OK? I see everything checked on except the bulbs.

EDIT: Oops, nvr mind. I see the next-to-last paragraph in the first post now..... I'll get my hat. Bye.

 

[jtnwevo]

Well, it is not the brake light relay. Replaced it and still no lights. I tested the wires at the relay and get +12v where it should and switched 12v where it should when I actuate either brake switch. When I apply 12V to the output line the YCCS relay clicks but I still dont get brake lights. Is that normal? YCCS was working just fine before I tore into this.

Maybe I just have a broken wire between the relay and the lights? I am going to remove the front cowling so I can get better access to the wiring and may just have to run new wires from the relay to the lights.

Any ideas?

Thanks

JT

 

[mcatrophy]

Well, it is not the brake light relay. Replaced it and still no lights. I tested the wires at the relay and get +12v where it should and switched 12v where it should when I actuate either brake switch. When I apply 12V to the output line the YCCS relay clicks but I still dont get brake lights. Is that normal? YCCS was working just fine before I tore into this.
Maybe I just have a broken wire between the relay and the lights? I am going to remove the front cowling so I can get better access to the wiring and may just have to run new wires from the relay to the lights.

Any ideas?

Thanks

JT

Could be the diode shown in my diagram above, or its connections. I don't know where that diode is, though. Possibly just hanging in the loom somewhere. Don't bypass it with a wire ("run new wires"), you'll upset the operation of the ABS and/or the Y-CCS computers.
[Edited to add pictures of my '06 FJR1300AS]

These picture show two diodes taped together, I don't know if the brake line one is red or black, but it's got the yellow wires going to it.

(Click on image for larger view, 2nd one is very large to get the detail)

Held up and showing wires (bottom of pic)

 

[jtnwevo]

Thank you sir. That gives more ideas of what to look at once I get the front cowl off.

 

[jtnwevo]

Well, it was one of the two diodes that lives up front near the battery. I replaced them both so I am not sure which it was for the brakes. Strange thing is in both cases the new and old diodes responded the same to tests on my multi-meter. Now I gotta put it all back together.

2 front diode part numbers:

5VG-81980-00-00
4WA-81980-00-00

Thanks all for the suggestions and special thanks to mcatrophy.

 

[mcatrophy]

Thanks for posting the fix, and glad to help.

Could it have been a dirty or corroded connection, cleaned by changing the diode?

 

[Constant Mesh]

Why have a brake relay energized all the time except when the brakes are applied?

Seems a bit strange. Definitely not energy efficient.

Maybe some "fail safe" safety advantages.

The always energized accessory box solenoid is another questionable energy hog. A constant 7 watt drain.

 

[YummYam]

So, recently discovered had no brake lights and searched the forum for possible causes. The relay was clicking but apparently that can be a red herring. Took a deep breath and started to investigate yesterday.

Imagine my relief when after taking the seat and smuggler off and wiggling some wires, the problem turned out to be my amateur ground wiring connection effort when installing the Admore lighting in the G47 box and took all of ten minutes to rectify.

Phew! Could have been much worse as depicted in these posts, but thanks anyway guys for posting your own experiences to help others.

Steve