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Old 12th July 2005, 11:34   #1
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Default Limp home modes?

Most cars in india until a few years ago were pretty mechanical and some are still so. So faliure is incremental allowing you to limp home. For example your fuel supply may miss, your power steering may fail but you still have manual control etc., With the new fly by wire cars with one ECU handling everything what happens when the CPU dies? Do modern MPFI ECU /wire controlled cars have a limp home mode or you can be stranded at 100kmph with no brakes or your engine dying on a remote stretch because the ECU died? Unlike mechanical parts electronics can fail in one shot. Anyone have such an expirience of electronics dying on a lonely stretch with no help in sight?
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Old 12th July 2005, 11:42   #2
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hi, yes the new cars do have a closed loop setting in the ecm....comes into play when some electronics fail in the car...the check engine light comes on and lets you drive the car in a pre-set map or closed group setting.
this allows it wwhen certain sensors fail....

happened to me when after tinkering with the car i forgot to connect the MAP sensor ...car used to idle funny and then after 2000revs became smooth...kept scratching my head till noticed the mistake....

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Old 12th July 2005, 11:47   #3
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If some electronics fail. Thats the catch. what if the ECU fails. For example the processor can die. What happens then. think of a scenario where the accelerator is connected to a wire which goes to ECU and the processor decides how much fuel to supply. If processor dies does the car go into a 2000rpm mode or something like that. Now if the brakes are also controlled that way, what happens? There is a thread about unreliable machines where fuel pumps have died leaving owners stranded. Any of this forum owners faced this? I read a thread about a ford Ikon ECU death where the car wouldn't start.
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Old 12th July 2005, 12:49   #4
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I guess if the ECU fails, there is no chance of limping home.
In fact police in USA, use a small skateboard like vehicle which goes under the car and delivers a shock. Scrambling the ECU and the car.
Still a prototye I think
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Old 12th July 2005, 13:15   #5
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Quote:
I guess if the ECU fails, there is no chance of limping home.
In fact police in USA, use a small skateboard like vehicle which goes under the car and delivers a shock. Scrambling the ECU and the car.
Still a prototye I think
And didn't they show a similar gadget in 2Fast 2Furious, where they shoot a sort of electronic tranquilizer which clings on to the car and brings it to a stop.

Not sure if they're used in real life but, no doubt it'l happen in a few years.

The Honda manual says that the moment you see the engine warning light, stop the car and call the nearest Honda service station.

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Old 12th July 2005, 16:05   #6
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some cars run even if the ecu fails.....goes into a lock mode
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Old 12th July 2005, 17:38   #7
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The only cars that has Electronic brakes(that is the Mercs) also have a mechanical link up to the front brakes.so even if electronis fail one can still bring the car to a halt.
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Old 12th July 2005, 18:41   #8
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All brake system have a built in failsafe. They're all electro-hydraulic systems, so if the electro fails, the hyd. still works, albeit with more effort and less extra functions.
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