ABS & ESP warning lights

[Mad smart person]

Greetings All, I have a 2005 Fortwo Brabus, recently, the above two warning lights have been annoying me. On start up, they behave as they should. They light up with all the other warning lights and go out as they should, they remain out, after engine start untill I apply the footbrake for the (usually) first time, then on releasing the brake these two lights light and remain on untill I stop the engine and start again, then the process repeats. For this to happen the car does not need to move under its own steam. IE, start the engine, all is well, gearbox in neutral, car not moving, apply foot brake, release brake both abs & esp lights come on. There are a couple of variations on the problem. On a hot day, yes when the sun is out, the ABS & ESP lights behave for maybe 10 miles, then they come on after foot brake application. If before starting the engine, I apply heavy pedal pressure and pump the pedal hard as well, the lights will behave themselves for a short time but then they light and remain on.
I've checked the fluid level in the reservoir and that's fine. The reluctor rings look fine. The tyres could be a problem and am working on another set to fit and compare. I am wondering though about the thoughts on the brake pedal switch being the problem. Can anyone tell me why this should be when, the brake lights and gear change work as they should. Also there seems to be some that suspect the YAW sensor? Would turning this through 90 degrees help with diagnosis? Any other thoughts on the problem please. Cheers, Ian.

[137699]

Your Brake Pedal switch needs replacing. Reason why your brake lights & gearbox still work? Well, as has been said many many many many times, the brake pedal switch is 2 switches in one. So one fails while the other continues to work.

[Mad smart person]

Greetings 137699, thanks. There are actually 5 wires that go to the switch, I've wondered what the 5th wire was for? I've assumed that one set of contacts, the 'NO', was for the brake lights and the 'NC', for the SE unit to change gear. I've another question, the level sensor in the brake fluid reservoir, is that a capacitive device? I measured the resistance and it appears to be open circuit, which would indicate a non-resistive device? I did the measurements on a reservoir that was not attached to the car so was able to turn it up side down. It was working prior to removing it. Sadly, all of this proves to me that these cars are too Smart for their own good. Any further idea's on the problem at hand - other than me..... Cheers, Ian.

[Evilution]

There are actually 5 wires that go to the switch.

You are using the word "actually" wrong, lol. There are only 4 wires to a standard smart brake light switch.
http://thumbs4.ebaystatic.com/d/l225...VXCbYI0iyA.jpg

[Mad smart person]

Greetings RC, OK, so what is the fifth wire for? There are 2, 20g wires and three 24g by the looks of things. What makes a non-standard brake light switch then? Cheers, Ian.

[Mad smart person]

Greetings all, RC, I think I've sent you a PM. If not, here's a photo of the switch and its attached wires. Any thoughts, greatly liked. Cheers, Ian.

[Evilution]

Do all of the wires go through the electrical tape to the switch?
Disconnect the electrical connection and see how many pins.
I can't see any reason why there'd be 5 wires.

[Mr T]

Looking at that picture, it looks like two of those wires are the same colour. Could be they are just using the connector as a splitter to feed to somewhere else.

[tolsen]

Very curious. I guess we'll all be counting our brake light switch wires.

[Mad smart person]

Greetings All, yes, all the wires go through to the plug/switch. I'd suspect that the plug is being used as a 'splice' joint for the '5th' wire to go somewhere else, rather than have a splice along the wire run. I'd like to know where that wire goes or what signal it's providing to what? It's not the only brake light switch I've seen 5 wires going to it. Sadly, although I'm most keen to drop the belly panels (I'm not being sarcastic here) I've shagged my right shoulder and would probably fail a drugs test with what I'm on at present. So, for the time being, I'm lying low - pun not intended. I shall though let you all know the out come, when I have one. At this rate, probably next year - bugger. All I ask is, think of me when you're enjoying your Xmas tipple. Anything with inkahol (see what I mean about the drugs test) in it, is off the menu - double bugger. So, next year I'll be able to get into my favourite tipple, Flaggpunsch.
What I can't get my head around, even without Meds, is the problem that the brake lights & gear change work as they should.
Does the ABS/ESP sense brake line pressure when your foot is on the peddle and hence maybe a difference in pressure, say with air in the line??? Although, 'pumping' the peddle would cause the air to defuse into the fluid, the fluid would still have a different pressure due to the air being defused. Cheers, Ian.

[137699]

What I can't get my head around, even without Meds, is the problem that the brake lights & gear change work as they should.

Is it really that difficult to get your head around? Did you not read my reply (#2 on this thread)? There are TWO switches in the unit. One controls brakelights & reverse selection, the other sends signal to the ESP system.

Guess which one has failed on yours? (hint you are getting ABS/ESP lights on the dash, but your brake lights are working)

[dervsmart]

The most likely reason there are 2 switched circuits in the single brake light switch is that the bulbs require 12v to operate and the ABS control unit would require a 5v signal as it's a computer, so the 2 switches are electrically separate.

[Thrumbleux]

is the problem that the brake lights & gear change work as they should.
Does the ABS/ESP sense brake line pressure when your foot is on the peddle and hence maybe a difference in pressure, say with air in the line??? Although, 'pumping' the peddle would cause the air to defuse into the fluid, the fluid would still have a different pressure due to the air being defused. Cheers, Ian.

The switch is only required to select gears while stationary. Once moving it plays no part in gear selection. If it causes you to be unable to select 1st gear - just nudge the lever forward and 1st will engage.
Installing a new switch requires accurate positioning of the switch re travel. Yours may be out of adjustment hence heaving on pedal having an effect.
Your experience of it being better behaved on warm days may point to moisture ingress - something they are prone to with careful routing of the wires required to circumvent.

[Mad smart person]

Greetings all, thanks Thrumbleux, finally some explanations of why. Yes, I do know there are two sets of contacts inside the switch, one NO, the other NC. Without a wiring diagram it's not easy to figure out what's going on - given the cars are assembled in France. Yes, one pair of wires to the switch are 20G, hence assumed for the brake lights. The other pr, 24G, hence assumed for the gear change 'enable'. I'd now suspect that the 5th wire heads off to the ABS computer. Sadly, the defect is intermittent, the worst type of defect as usually when you play with it, it comes right for about 2 days.
The possibility of liquid ingress is good, as is the adjustment of the switch. I shall be doing a bit of testing to prove one way or the other. Even switches are innocent, until proven guilty. I shall also insure there's a drip loop in the wires before they get to the switch. For those that have removed the belly panels, I'm sure you'll agree, it's not the sort of job you want to be doing twice in a week. Particularly as I don't have access to a hoist.
As my shoulder is still knackered, I won't be getting in to this for a week or so. Probably next year now. Good things take time.
Cheers, and Merry New Year. Ian.

[Thrumbleux]

Even switches are innocent, until proven guilty.

Not that b#stard! Just replace it. It aint worth faffing with especially...

.

For those that have removed the belly panels, I'm sure you'll agree, it's not the sort of job you want to be doing twice in a week.

as you say, working with the undertray (lower it only though - no need to remove) is a PITA. It will be the switch at fault. Just replace - and give your shoulder a rest!