brake lights help
 

Current symptoms: brake lights not working, abs and stability control not working, no CEL, speed sensors work.

Replaced the brake light switch under the the pedal and still had issues. When I remove the brake light switch I was told the brake lights were supposed to come on and they don't, which makes me think I have a blown fuse somewhere.

Thoughts? I hate everything electrical so I'm not entirely sure where to start on the wiring diagrams.

Thank you.

Edit: taillights are aftermarket toms v2, the parking lights work fine

If testing the switch, the lights should illuminate when the terminals make contact, not when they are separated.

Or is that what you were trying to say?

First unplug the lights and focus on ABS. I say that because I'm assuming one of your brake lights failed by shorting out.

I was told when the brake light switch is removed, the lights should turn on. Is that incorrect?

As of right now the lights don't do anything whether or not there is contact or not. Sorry if I was a little unclear.

Switch shows normally open on the lamp side, normally closed to the ECU. Unplugged lights will be off, ECU will show off as well. Switch should test O.L on pins 1-2, 0.0 on pins 3-4. Unplugging the switch will set a fault since the switches can never both be open.


Fuse is at the top left, 7.5A.

Power goes through the noise filter, out to the stop lamp switch and back in. Then out to the grey distribution on the bottom left, to the modules and physical lamps.

Triangle lines on the bottom row are grounds. Lines that cross with no dots are not connected, lines that intersect with a dot are connected.

I would start with that fuse, labeled STOP.

Thank you, @maslin. I just noticed that the third brake light is also suspect. If the fuse is blown, one of those lamps or the wiring is shorted.

Agreed. Assuming the fuse is blown, I would unplug the lamps, replace the fuse and go from there. Keep in mind the codes may need to be cleared before the warning lights go away, and not with a generic OBD II scanner.

Blown fuses and aftermarket electrical parts kind of go hand in hand.

Modern stop lamp switches are redundant. One side normally open, one side normally closed. Both signals go the the ECU.

Unplug the switch, both sides go open. Value is implausible and a fault is set.

1-2 is normally open, 3-4 is normally closed. When you actuate the switch 1-2 goes closed, 3-4 goes open, lights come one, ECU knows the switch is actuated. Any deviation from one open one closed sets a fault.

Winner winner chicken dinner!

blown fuse, probably caused by the taillights. amazing how a tiny thing can cause such a massive fuck up.

just double checking the fuses labeled "spare" are in fact spares correct?

Correct. Just be sure to replace the spare soon!

Also, I'm concerned about why the fuse blew in the first place-fuses are incidentals, not causes. I wouldn't consider the issue corrected until the over-drawing device is located. Is there moisture in either taillight?

@Ultramaroon called it before I did. Good that it’s going again, but whatever blew the fuse will probably blow it again.

Anything unusual lately? Water in the lights, lots of traffic, etc? Went out one morning and all the lights were on, or they came on after a particularly deep hole in the road?

As @soundman98 said, fuses blow when they are over loaded. On a circuit that shouldn’t vary too much (should be the same draw every time) the fuse should be fine.

If the fuse blows again I’d start with the lights, could be a wire rubbed through or third brake lamp as well. I don’t see it being a module, just a reference signal going out to those.