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Discussion Starter #1
The traction control light comes on intermittently when driving my 2011 manual Lotus Evora. It doesn’t have a sport button so there doesn’t seem to be any consequence to driving the car when the light goes on. I tried to fit it by replacing the brake sensor without any luck.
1. Anything else to try to fix it?
2. Does the Lotus dealer have any special abilities to diagnosis the problem compared to a normal mechanic? I don’t have a local dealer (closest is in Seattle 170 miles away since unfortunately my local dealer dropped their franchise). I’m going up to Seattle for two weeks in April so could drop it off if there’s a good chance they could fix it. The light doesn’t always go on, particularly when first driving the car so I don’t want to bring it if they can’t do anything.
3. Is it dangerous to bring it to the track without fixing this problem? I signed up to do a high performance driving class in May.

Thanks for any advice.
 

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Do a search for brake sensor switch. It’s a likely culprit.
 

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Many owners have solved traction control light/loss of cruise operation with a brake light switch replacement. So, this may have been or still be your issue. Although a replacement switch just popped in usually does the trick, it might not be set up for the particular vehicle (proper adjustment and number of clicks on the plunger).

The dealer has the ability to refine the adjustment via TechCentre (and also check for any codes if you have not done so already) so it may be worth a stop in to see them during your Seattle trip if you can't get it sorted:

"Note: Incorrect switch plunger adjustment may result in fault codes relating to ABS, Lotus DPM (Dynamic Performance Management) and cruise control being generated also illuminating the relevant tell tale lamp.

The switch plunger uses an internal ratchet mechanism which can be adjusted to suit the vehicle allowing for any brake pedal travel tolerance thus ensuring the correct phasing of the internal switch contacts in relation to the switch plunger position and brake pedal position.

Refitment Procedure

With TechCentre connected to the vehicle and the ignition on, select ABS brakes> Live Data:
From the ‘Available Items’ table, select:2.
Brake light switch (03). -
Brake switch. -
Pressure sensor -"

etc. etc....

Also note that there was a switch plunger lubrication TSB 2015/03:

"TITLE:
Application of silicone grease to brake light switch plunger to improve durability.

REASON:
Several instances of brake light switch renewal under warranty have been reported due to the illumination of the ABS (Anti-Lock Braking System) tell tale lamp accompanied with the generation of diagnostic trouble code C0340 - brake light switch.
Investigations carried out by Lotus on returned switches have not determined any specific internal electrical faults, though some switches exhibited sticking plungers which, under certain conditions would have caused this trouble code to be generated. Furthermore lubrication with silicone grease of the plunger sections of ‘failed’ switches has resulted in them successfully completing durability testing with no further fault code generation.

ACTION:
Use Lotus TechCentre to diagnose if any specific sensor, switch, harness connector etc is an obvious cause of failure in the event you are presented with an Evora, Exige S or Elise (‘11MY onwards fitted with a Bosch ABS module) that has generated fault code C0340.

Regardless of the fault found and rectification work carried out (even if the fault was not caused by the brake light switch) a small quantity of RS 494-124 silicone grease should be applied to the switch plunger as shown in the RH illustrations and procedure listed below:

A. Apply the equivalent of a ‘pin head’ amount of silicone grease to either side of the plunger at the base of the switch body and evenly distribute along the complete length of the shaft.
B. Fully actuate the plunger (if switch not yet fitted to the vehicle) to allow the grease to travel inwards into the switch body ensuring the internals of the switch mechanism are fully lubricated*.

Silicone grease should be applied if fitting a new service replacement brake light switch, but if carrying out this procedure to the existing switch in-situ*, ensure the plunger is actuated by ONLY depressing the brake pedal repeatedly and use the application nozzle supplied to accurately apply the grease**.

*Care points: Manually operating the switch plunger by hand whilst in situ may activate the plunger ratchet, altering its length, requiring the brake pedal to switch to be re-set to avoid generating additional fault codes.
Ensure that silicone grease has not spilt onto any of the pedal pads, as a precaution cover the pedal pads prior to carrying out this procedure. Check and clean the pedal pads as necessary after completing this procedure.
Continued

**Only RS 494-124 silicone grease should be used for this procedure, other silicone greases may cause damage to the internal electrical components of the switch. RS 494-124 silicone grease is readily available in 100g tubes and can be sourced locally."

For the time being, you could try readjusting it slightly (midpoint is 5 clicks out) and see if it helps... good luck.
 

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Also happened to me. Dealer replaced the brake light switch as the plunger lost any spring it had. I also ordered and carry the one from GRP as a spare ($20) as I already ruined one road trip track day because of the first failure.
 

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Discussion Starter #5
Thanks 2011 chrome orange for the detailed info. I will see if I can try adjusting it at home and if no luck bring it to the dealer in Seattle in April. I noticed that the plunger part while fitting into the bracket is at a slight angle so perhaps there is a way to adjust it for a better fit.

Perhaps the fault happens when the sensor plunger isn’t depressed when I press down on the brake pedal. Perhaps it the plunger isn’t tightly aligned and completely vertical it can give this behavior.
 

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Discussion Starter #6
Figured out that the length of the plunger was adjustable as described by 2011 chrome orange — included pictures in the how to thread. Seems working tonight in the garage and will see how it works tomorrow on the road.
 

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Figured out that the length of the plunger was adjustable as described by 2011 chrome orange — included pictures in the how to thread. Seems working tonight in the garage and will see how it works tomorrow on the road.
Can you feel a little bounce while pressing the plunger? If it moved out a few clicks but has to spring to it, it may work for a little while but will still fail. At least that was my experience.
 

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Discussion Starter #9
it seems like the plunger was well aligned (and the rear brake light illuminated appropriately when pressing the brake pedal) but the traction control light went on sooner and stayed on for the entire drive today whereas before it would just be intermittent. Also new is the yellow wrench (indicating electric fault tell tale) now illuminates when the car it started. This had never illuminated before. Next is more internet research and if no luck I will take to the Seattle dealer in April.
 

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it seems like the plunger was well aligned (and the rear brake light illuminated appropriately when pressing the brake pedal) but the traction control light went on sooner and stayed on for the entire drive today whereas before it would just be intermittent. Also new is the yellow wrench (indicating electric fault tell tale) now illuminates when the car it started. This had never illuminated before. Next is more internet research and if no luck I will take to the Seattle dealer in April.
I also got the wrench once on a road trip. I cleared the code and it never came back. Good Luck.
 
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