Brake pedal sensor - effect of failure

[TdM]

So, I've got the good old TC and ABS lights on. As it's the middle of winter, difficult to get a garage that's ready to deal with it and I need the car, do we know if it fails 'Safe' or fails 'dangerous' i.e. are all my driver aids on or off?

 

Save doing some enthusiastic (and possibly dangerous) testing, I thought I would check if anyone knew.

[Bruss]

If its a warning light I’d have a guess it fails with it not working. I don’t know whether it could ‘fail’ and still be working.

[exeterjeep]

When I had problems with mine it was not on all the time, and on one occasion I drive around 40 miles after it triggered without noticing anything untoward.   

It was only when it seemed to come on all the time that I changed it. I followed the instructions I found and did it myself. Would have been better if I had read all the instructions as it would have been easier. I bought the part some months before I changed it. 

Obviously this assumes yours is  the brake pedal switch and not something else.

 

[Rambo]

Why not diagnose the fault with a good OBD 11 reader? I reckon they're a useful bit of kit for any Evora owner. It has saved me many hundreds of ££££

Edited December 19, 2023 by Rambo

[Bruss]

I can’t remember now but I’m not sure the obd diagnosed it. I had a flickering warning light and replaced the switch after reading about someone else with the problem.

[TdM]

Yeah, the OBD reader shows no faults. Not the best state of affairs to drive around in winter with no driver aids, the rain this morning for example!

I'll order a switch and have a go at changing it, doesn't look too bad from the internet searches as long as I get the right part. PITA that it happens at Christmas time just after our other car got nicked!

[exeterjeep]

2 hours ago, Rambo said:

Why not diagnose the fault with a good OBD 11 reader?

which reader would access this area of the car(apart from a Lotus one)

[Rambo]

Sorry, I meant use a good OBD 11 reader to discount and erase any other fault codes that may exist.

[Whitey]

When I have had this fault, it is intermittent and the first that happens is that it drops out of Sport mode and you get the TC and AB’s lights on. I have normally found that this happens if you are just using the car lightly and hardly touching the brakes. Mine will normally clear itself after the first restart. If using the car harder, incl the brakes, it doesn’t seem to happen on my car. I bought a new sensor a few years ago and have never fitted it as the fault quickly clears and I make habit of using the brakes harder than normal periodically and that keeps it away.

I would try a few restarts, if it clears, take it for a decent run and hit the brakes a few times. Works for me anyway 😀

[DH2]

19 hours ago, TdM said:

So, I've got the good old TC and ABS lights on. As it's the middle of winter, difficult to get a garage that's ready to deal with it and I need the car, do we know if it fails 'Safe' or fails 'dangerous' i.e. are all my driver aids on or off?

It fails off - it cannot fail on if the sensor it uses to operate isn't working!

[TdM]

Well, it's had a new sensor and the lights are still on. I suspect the issue is actually something relay related, some clicking can be heard randomly coming from the back seat area... I'll update when I find out what is causing it

[Bruss]

Your post title said it was the brake sensor. Did you consider the clutch sensor? This can give the same flickering light. 

[TdM]

Thanks Bruss. I didn't know that could cause the same lights to come on. You might be onto something as the car is very lumpy after clutch engagement in second as well, which would marry with the clutch sensor.

[exeterjeep]

When I had this problem the dealer thought it could be a wheel sensor. (ABS?)

[Jovver]

I had the TC and ABS lights coming on as well, but bizarrely it turned out to be a symptom of a dying battery..

[TdM]

It shouldn't be the battery it's about a year old and gets regular use. I'm feeling confident about Bruss' suggestion at the minute

[Phaeton91]

To test if the ABS is still working perhaps find a clear wet muddy lane and slam on the brakes.  

[DH2]

Optimal answer is to get the ABS codes read! (I appreciate that may not be easy over the holiday period)

I'd definitely be investigating any relays clicking in the rear fusebox, I've not come across that before.

It could still be a mal-adjusted brake pedal switch.

Dave

[exeterjeep]

28 minutes ago, DH2 said:

It could still be a mal-adjusted brake pedal switch.

when I did my switch, I had the spanner symbol, adjusting the plunger steps sorted it and spanner went away after a number of re-starts.

[2011 Chrome Orange]

The car has to be happy with the brake switch position. Lotus states to start at 5 clicks out (of course, they set it up while hooked to their computer). For the rest of us, its trial and error to get it correct.

My first replacement switch made the car happy with the plunger at 5 clicks. My last two switches needed 7 clicks out for the car to be happy.

If the issue was the brake switch and you have it to the  proper setting, the lights will go out after the 5th key cycle.

[EuropaSman]

From the Service Notes.

[TdM]

SWLotus have found the problem.

A piece of rust in the ABS ring. A very quick fix but not the quickest thing to find. Worth putting on the checklist if you have a similar issue.

[Whitey]

Not heard of a abs ring, where about is it located?

[Bruss]

Unusual failure. Located on the end of the driveshafts usually. Quite where on the Evora I’ve never had to investigate.