Why on earth? Blown bulb turns off ABS and TC.
Discussion
So, happily driving along in my commuter mobile, enjoying a bit of 80s hip hop (cos I am soooo gangsta), when the brake warning light comes on, the ABS light comes on and the 'traction control - off' light comes on. s
t, thinks I, big problem somewhere.
Quick check, and whilst the ABS and traction control might be off, the brakes definitely still work fine, so decide to finish my journey and sort it out on arrival.
Shortly thereafter, a kindly fellow motorist points out to me that my port and starboard brake lights are not working, with only the high level repeater still showing under braking. So - divert to Toyota dealer, pick up a pair of bulbs for the princely sum of £1.40, change same and hey presto - dash lights all reset and everything works again.
Now - whilst I appreciate the car letting me know when there's a problem, why the fk does it turn off the ABS and traction control just because the bulbs have blown!? Seems a very odd thing to do, and, if we accept that ABS and TC are there to increase my safety on the roads, it's arguably putting me and other motorists at greater risk.
Is there a rational reason for this, or is it just an odd set up? Perhaps a catch all 'yikes, somethings wrong, turn it all off!!' switch?
t, thinks I, big problem somewhere. Quick check, and whilst the ABS and traction control might be off, the brakes definitely still work fine, so decide to finish my journey and sort it out on arrival.
Shortly thereafter, a kindly fellow motorist points out to me that my port and starboard brake lights are not working, with only the high level repeater still showing under braking. So - divert to Toyota dealer, pick up a pair of bulbs for the princely sum of £1.40, change same and hey presto - dash lights all reset and everything works again.
Now - whilst I appreciate the car letting me know when there's a problem, why the fk does it turn off the ABS and traction control just because the bulbs have blown!? Seems a very odd thing to do, and, if we accept that ABS and TC are there to increase my safety on the roads, it's arguably putting me and other motorists at greater risk.
Is there a rational reason for this, or is it just an odd set up? Perhaps a catch all 'yikes, somethings wrong, turn it all off!!' switch?
It's a safety thing!
The ABS system uses the brake pedal switch as a CRITICAL input to tell it when you are actually applying the brakes. As such, any fault in that system could have significant consequences to the operation of the ABS/ESC system. Therefore, any fault in the brake switch/lamp system is designed to disable the ABS/ESC immediately for your safety!
The ABS system uses the brake pedal switch as a CRITICAL input to tell it when you are actually applying the brakes. As such, any fault in that system could have significant consequences to the operation of the ABS/ESC system. Therefore, any fault in the brake switch/lamp system is designed to disable the ABS/ESC immediately for your safety!
Max_Torque said:
It's a safety thing!
The ABS system uses the brake pedal switch as a CRITICAL input to tell it when you are actually applying the brakes. As such, any fault in that system could have significant consequences to the operation of the ABS/ESC system. Therefore, any fault in the brake switch/lamp system is designed to disable the ABS/ESC immediately for your safety!
Interesting the different inputs and effects isn't it! Presumably the thinking is that if there's an open circuit somewhere in the brake light system there's a chance that the pedal switch might not operate.The ABS system uses the brake pedal switch as a CRITICAL input to tell it when you are actually applying the brakes. As such, any fault in that system could have significant consequences to the operation of the ABS/ESC system. Therefore, any fault in the brake switch/lamp system is designed to disable the ABS/ESC immediately for your safety!
Surprised they don't incorporate pressure sensing into the ABS/ESC blocks though.
Krikkit said:
Interesting the different inputs and effects isn't it! Presumably the thinking is that if there's an open circuit somewhere in the brake light system there's a chance that the pedal switch might not operate.
Surprised they don't incorporate pressure sensing into the ABS/ESC blocks though.
In the business it's called the "interdependability matrix" and it rapidly gets very very very complicated on modern cars with CAN bus communication!Surprised they don't incorporate pressure sensing into the ABS/ESC blocks though.
Pretty much every ABS system also uses master cylinder pressure as a second input, both for validating the brake switch(s) and for applying variable control gains. However, when an input source is lost or unreliable, the best course of action is to suspend operation of the critical systems and flag that fact to the driver (ABS lamp illuminates etc).
(Because it doesn't know why or what the fault was caused by. For example, no brake lamps could be a blow fuse, blown bulb or wiring shorting to ground, or faulty/intermittent brake switch, any of which can make a right mess of critical control logic execution)
Edited by anonymous-user on Friday 1st August 16:59
DrDoofenshmirtz said:
More likely it just sensed the blown bulbs and the dash lights were a warning to get you into the garage.
Frankly, I don't think a sodding great big dayglo balloon bobbing around, tethered to the bonnet, with "YOUR CAR WILL EXPLODE IN THE NEXT THIRTY SECONDS IF YOU DON'T FIX IT!" would get half of our fellow "vehicle operators" to do more than go "Meh. MOT's in eleven months. They'll sort it then."This happened on my 1991 Honda Prelude, brake light out caused the ABS to fail and give a warning on the dash. However when I had a blown bulb on a 2002 Honda S2000 I didn't notice any warnings or ABS problem so I guess they changed how the system is designed to respond the bulb failure.
HertsBiker said:
There's no way both bulbs went at the same time so you've been without one bulb for a while.
It does sometimes happen - happened to me with dip beam once. I'd driven somewhere in the dark, parked - both definitely working. Came out, got in the car, turned the lights on - they went bright, dim, bright, off. Both dip beam bulbs had blown - I'd replaced one when I bought the car a couple of years earlier, and both replacements were fine from then on until I sold the car several years later...Mr Sparkle said:
This happened on my 1991 Honda Prelude, brake light out caused the ABS to fail and give a warning on the dash. However when I had a blown bulb on a 2002 Honda S2000 I didn't notice any warnings or ABS problem so I guess they changed how the system is designed to respond the bulb failure.
I had the same on my Prelude (I still miss the car after 15 years). Late 80's Hondas did do some odd things. I had a 88 Aerodeck and the headlamp washer pump burned out due to frozen water in the bottle - it took out one headlight bulb and the headlamp motor control on the other side. I had to wind up the light manually every time I restarted the car.
PS I once owned a Yaris Mk 1 that commuted from Kensington High street to Sevenoaks via the local city slog to the A3 and M25 each day. It was the hardest drive for a Yaris in the UK as about a gazillion gear changes every trip. It did 75 000 miles doing this, or 3 times around the world.
The funny thing was the engine warning light came on at about 4000 miles. I took it to the Toyota dealer and they said it was just the sensor. They reset it. After 1 mile from the dealer it came back on. I just ignored it as it was a Toyota, I knew it would hang together. For 5 years it always did the same thing, they would reset it and about a mile later, with a grin on it's electronic face, it came back on. So I drove 75 000 miles with the engine warning light on, this must be a record.
It finally got taken out by a van with a young man driving it like the clappers who was lost and decided to just change direction without using the mirrors.
The mark 1 Yaris was a fantastic car. Lift off oversteer also in the wet around M25 junction 5 anticlockwise too. Triffic.
I miss it.
The funny thing was the engine warning light came on at about 4000 miles. I took it to the Toyota dealer and they said it was just the sensor. They reset it. After 1 mile from the dealer it came back on. I just ignored it as it was a Toyota, I knew it would hang together. For 5 years it always did the same thing, they would reset it and about a mile later, with a grin on it's electronic face, it came back on. So I drove 75 000 miles with the engine warning light on, this must be a record.
It finally got taken out by a van with a young man driving it like the clappers who was lost and decided to just change direction without using the mirrors.
The mark 1 Yaris was a fantastic car. Lift off oversteer also in the wet around M25 junction 5 anticlockwise too. Triffic.
I miss it.
Gandahar said:
The funny thing was the engine warning light came on at about 4000 miles. I took it to the Toyota dealer and they said it was just the sensor. They reset it. After 1 mile from the dealer it came back on. I just ignored it as it was a Toyota, I knew it would hang together. For 5 years it always did the same thing, they would reset it and about a mile later, with a grin on it's electronic face, it came back on. So I drove 75 000 miles with the engine warning light on, this must be a record.
Penny? Its you, isnt it?http://www.youtube.com/watch?v=KMhp2ShPVQw
HertsBiker said:
There's no way both bulbs went at the same time so you've been without one bulb for a while.
Good point; and I've had one go before so I know that doesn't cause the same dashboard Christmas tree effect. So - why not do it for just one bulb blown? Curiouser and curiouser.thismonkeyhere said:
Good point; and I've had one go before so I know that doesn't cause the same dashboard Christmas tree effect. So - why not do it for just one bulb blown? Curiouser and curiouser.
Because the circuit is still complete as the two bulbs are in parallel?Once the second one goes the circuit is broken and all the stuff that needs input relating to that circuit goes into spaz mode?
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