[arrowaby]

Hi Guys!

This is with respect to my Hyundai i20 Asta diesel.

Fact: The tail lights wont go off even if the car is totally off. It just stays on throughout.

Observation: Driving the car in this mode is weird because the onboard computer, perhaps, detects that the driver is braking (since the tail light is on), and then pauses the fuel outflow into the engine (replicating a normal braking exercise) causing a sudden dip in acceleration when I am driving straight and have no intention of braking.

This feeling can best be described like that particular point when you are riding your bike and it suddenly moves into "Reserve Fuel" state when there is a sudden dip in acceleration due to an empty fuel tank.

In such a scenario, I released the accelerator quickly and pressed it again to resume the fuel supply.

Temporary Hack: I immediately opened up the control panel below the steering wheel and with the help of the User Manual identified the fuse that is linked to the rear tail light and pulled it off.

So temporarily the tail lights are permanently off and the dip in braking issue has been sorted. However the tail light fuse is also linked to the power-windows system. Hence, the power windows wont work now until I plug in that fuse again.

Help

[Akshay1234]

Why not just visit the service centre? It will most probably be the brake light switch which is behind the brake pedal.

[Viju]

Definitely looks like a BLS (Brake Lamp Switch) malfunction. Please visit a service center asap as it is more serious than just the brake lamps staying ON and draining your battery.

The BLS signal is used by multiple ECUs including ABS (which I assume your car is equipped with, since it is an Asta variant), and the ABS will not function without the signal from the Brake Light Switch.

Once the fault is rectified, please ensure that the error codes of all the controllers are checked and cleared.

[Nik2772]

Originally Posted by arrowaby

Fact: The tail lights wont go off even if the car is totally off. It just stays on throughout.

Observation: Driving the car in this mode is weird because the onboard computer, perhaps, detects that the driver is braking (since the tail light is on), and then pauses the fuel outflow into the engine (replicating a normal braking exercise) causing a sudden dip in acceleration when I am driving straight and have no intention of braking.

This feeling can best be described like that particular point when you are riding your bike and it suddenly moves into "Reserve Fuel" state when there is a sudden dip in acceleration due to an empty fuel tank.

In such a scenario, I released the accelerator quickly and pressed it again to resume the fuel supply.

I have 2 questions :

1. Do the lights stay 'ON' all the time? I know it is a stupid question but that might be the case as they are powered directly by battery.

2. Did you notice that the lights are illuminated throughout the drive, or just guessing it because of the power drop?

Whatever is the problem, get it rectified from the service station. Going to FNGs doesn't make sense because they will prefer some short-cut to temporarily solve the problem.

Driving without the brake lights (as you would be doing now, though temporarily) is dangerous for you as well as others on the road.

PS. Did it have any adverse effect on the car battery?

[arrowaby]

Originally Posted by Nik2772

I have 2 questions :

1. Do the lights stay 'ON' all the time? I know it is a stupid question but that might be the case as they are powered directly by battery.

2. Did you notice that the lights are illuminated throughout the drive, or just guessing it because of the power drop?

Whatever is the problem, get it rectified from the service station. Going to FNGs doesn't make sense because they will prefer some short-cut to temporarily solve the problem.

Driving without the brake lights (as you would be doing now, though temporarily) is dangerous for you as well as others on the road.

PS. Did it have any adverse effect on the car battery?

I walked out of the office to the parking lot just to see my car tail-lights on. For the first time ever. Had never seen it before like this. On driving I experience the power loss hence I removed the fuse temporarily.
Also, I cant drive the car with the engine dipping power suddenly every 500-700 odd meters. Any driver behind me maintaining the same speed may collide because of my sudden speed variations.

Car battery is new so there was no adverse effect noted on that day or ever since.

I'm going to the service station tomorrow itself as I need to travel to Mumbai on Sunday and I can't keep opening the door and pay the toll every time since the power windows don't work now.
Shall post an update tomorrow/day-after post the repair.

[RSR]

Yes, please take the car to a good Hyundai authorized service centre.

I have also faced this issue once in our i10. It is very simple to fix and should cost very little.

It is indeed the brake lamp switch that is causing this problem. Cleaning it thoroughly fixes it for good! There is no need to replace the switch (unless it has gone kaput, which is very rare), just a proper cleaning would do the trick. I haven't faced the same issue again and it has been a couple of years now.

The issue seems more problematic in your i20 (affecting the acceleration) than it was in our i10, because the i20 is equipped with a "smart pedal" drive-by-wire system (in Hyundai parlance), when compared to the i10 whose "dumb" accelerator pedal is operated by a conventional cable.

When the ECU senses both brake and accelerator pedals are being pressed at the same time, the brake pedal gets preference and it ignores accelerator input, for safety reasons.

From what you have described, it looks like it is the brake lamp switch that conveys brake input to the ECU for the purpose of overriding accelerator input, apart from illuminating the brake lamps and high-mounted stop lamp. So the brake lamp switch performs a more important role in the "smart pedal" equipped i20 than in the i10.

Related Team-BHP thread on Brake Throttle Override:

http://www.team-bhp.com/forum/techni...-override.html

[Desmosedici]

This is definitely a Brake Light Switch Issue. I had faced this issue with my old Vtec. With wear and tear the switch breaks down and the contact point that gets pressed while braking stays there instead of coming off when you release the pedal.

A jugaad done by my mech was to fix a screw on the switch which resolved the issue and it never surfaced again. Try to see if you can do this temp fix and get going for the time being.

[Jaggu]

There is a switch that sits on the pedal and has some plastic piece that can break off, this causes the switch to stay ON all the while. Problem is this can drain the battery fully down, so get it fixed. Switch replacement is the solution and not very costly. In the interim while parking overnight, disconnect the connector of the switch (access it by bending down and checking), to avoid battery drain and tail light glass from melting.

[arrowaby]

Thanks for all the responses. I went to the Service centre and got he issue sorted.
As indicated by most of you, the Brake Light Switch was the culprit.
It seems that the part is repairable. The Engineer told me that he tried to repair it however the issue persisted and hence he replaced the part.

Total Cost : Switch Assy Stop Lamp Rs 865 + VAT 12.5% + Rs. 125 Labour.

[thoma]

Just noticed the same on an i10 and found that the brake lamp switch is actuated/de-actuated by the brake pedal, but a transparent 'plastic' part sits on the pedal which got brittle and fell apart. Without the plastic part, the brake pedal is not touching the switch. The switch is still functional in fact.

[bowser]

Originally Posted by thoma

Just noticed the same on an i10 and found that the brake lamp switch is actuated/de-actuated by the brake pedal, but a transparent 'plastic' part sits on the pedal which got brittle and fell apart. Without the plastic part, the brake pedal is not touching the switch. The switch is still functional in fact.

The exact same thing happened to my 1st gen Honda City recently. I noticed the brake lights were on and upon checking the brake pedal I saw the plastic part was missing. It had broken into several pieces and was scattered all over the foot well. I managed to find all the pieces, stuck them together with superglue and placed it back into the pedal. It's been 3 months now and still works fine.

[patel]

Do you mind sharing schematic of that transparent plastic part?

My accent has read this thread and is going through her part of this story: brake lights always on.

[decode]

Originally Posted by patel

Do you mind sharing schematic of that transparent plastic part?

Hi Patel, This can be due to a faulty Brake Light Switch or the plastic part on the brake pedal which touches the switch.

[patel]

Originally Posted by decode

Hi Patel, This can be due to a faulty Brake Light Switch or the plastic part on the brake pedal which touches the switch.

You are right. On closer inspection I did find crumbled plastic part (a very small nudge).
Since I was on highway, with lack of better alternate I choose to put a right sized bolt/screw in the gap created after the plastic part departed.

Is there any harm in keeping this metal replacement as long term solution? I went to few near by mechanics none seem to have that part.

[decode]

Your brakes will still work. There is a chance that the white plastic head on the switch can wear off quickly. I would recommend that you check with the authorized service center. Now that you know where and what need to done, it is a simple task.