Emergency stop (engine off) with Keyless Go? - Mercedes-Benz Forum

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post #1 of 49 (permalink) Old 10-18-2009, 01:53 PM Thread Starter
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Emergency stop (engine off) with Keyless Go?

I just finished reading the LA Times article today (10/18/09) regarding the runaway Lexus ES350 that went into unintended acceleration (up to 120mph) while driven by an experienced driver (19 year CHP veteran) and crashed killing all four of its occupants.

According to the article the involved Lexus ES350 has keyless ignition (similar to the MB Keyless Go or BMW Comfort Access etc. .etc) which prevent easily turning off the engine while driving. In the case of the Lexus, it requires continues holding the start/off button for 3 seconds to kill the engine in emergency situation.

What is the Mercedes procedure to turn off the engine while driving (in the case of emergency situation such as the unintended acceleration above). I tried to look in the car manual but could not find any reference to that case.

On a similar note with regard to the Lexus incident above, the driver (the veteran CHP officer) informed the 911 operator that the car has no brake, which according to the preliminary analysis is possibly due to the insufficient power brake assist (vacumn powered) under wide open throttle.

My question on the above case was wouldn't the activation of the brake reduce/close the throttle by means of the drive by wire (DBW) mechanism (in the case of cars equipped with DBW)

Any thoughts guy??

I have both BMW with Comfort Access and MB with Keyless Go and on both manual it does not say whether I can or cannot turn off the engine while driving under emergency situation.
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post #2 of 49 (permalink) Old 10-20-2009, 04:16 PM
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this is of interest to me also.
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post #3 of 49 (permalink) Old 10-20-2009, 05:50 PM
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This is very interesting. That makes me not like keyless ignitions even more.
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post #4 of 49 (permalink) Old 10-20-2009, 08:44 PM
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"Comfort Access" as you drive into a bridge abuttment. Is there no answer to this question? I think the cars need a big, red "emergency stop" button, like at the self serve fuel stations.
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post #5 of 49 (permalink) Old 10-22-2009, 07:58 AM
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my understanding and experience with non-mercedes cars is that on a regular KEYED car if you turn the engine off, the steering could lock and brakes would no longer be powered.
I wonder if the correct procedure/sequence would be to place car in neutral, maintaining steering/brakes and then pull over to a stop..then turn car off as normal.
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post #6 of 49 (permalink) Old 10-22-2009, 08:25 AM
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my understanding and experience with non-mercedes cars is that on a regular KEYED car if you turn the engine off, the steering could lock and brakes would no longer be powered.
I wonder if the correct procedure/sequence would be to place car in neutral, maintaining steering/brakes and then pull over to a stop..then turn car off as normal.
A good sound logical answer. Keyless go works the same way. If you switch the car off using Keyless go then you will loose braking power and the steering will lock, not a good idea. Place it in nuetral and brake before switching off and if the engine blows then so what. Better than having a serious accident.

ERIC.

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post #7 of 49 (permalink) Old 10-22-2009, 09:03 AM Thread Starter
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Actually in the case of keyed car, turning the engine off by putting the key in position 1 (acc) would kill the engine but not lock the steering wheel. Yes you will loose power steering, but the car is still steerable. You will loose brake assist but brake will still work which is still better than having to fight against the full power of the car.

Shifting to neutral is still the best choice, it seems. In the case of the Lexus incident in San Diego, the driver (based on the 911 recording) said that the brake was "not working". I wonder if he tried to shift the car to neutral but was unable or . . . .
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post #8 of 49 (permalink) Old 10-22-2009, 02:58 PM
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Actually in the case of keyed car, turning the engine off by putting the key in position 1 (acc) would kill the engine but not lock the steering wheel. Yes you will loose power steering, but the car is still steerable. You will loose brake assist but brake will still work which is still better than having to fight against the full power of the car.

Shifting to neutral is still the best choice, it seems. In the case of the Lexus incident in San Diego, the driver (based on the 911 recording) said that the brake was "not working". I wonder if he tried to shift the car to neutral but was unable or . . . .
In most keyed cars, you need to actually pull the key out of the ignition to lock the steering. But the issue here is not with keyed cars. It is with electronic controls. Given that the new transmissions are controled electronically, and not by hard rods to the gears, would they shift to neutral under hard acceleration? My service tech tells me that the transmission control module would read this as "not plausible". So, it seems that it would be possible that, under wide open acceleration, the trans would not shift to neutral. And, if the engine won't shut off, what's left? Don't forget... this would be a panic situation. You can't ponder these things as you careen down the road!
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post #9 of 49 (permalink) Old 10-22-2009, 03:36 PM Thread Starter
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On my E70 X5, I tried shifting my tranny (electronic shift) to neutral while driving regularly and yes it will go into neutral. I am not about to try the same thing under power as it might create an overrev condition but BMW might already put electronic "halt" on its tranny software which goes back to the issue that you might not be able to shift to neutral under power/max throttle.

I am just thinking can't the car manufacturer put like an emergency button which basically will electronically put the engine in "limp mode" (reduced power) to allow slowing down without loosing power steering or brake assist???
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post #10 of 49 (permalink) Old 10-25-2009, 05:36 PM
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for what it is worth.
my clk 350 with key less go WILL shift into neutral while accelerator is on the floor and vehicle is under full accelaration at highway speeds.
The car WILL go to redline when placed into neutral.
so it would seem that response would be same as a keyed car.
The car will go to redline but the individual would retain control of steering, brakes and have a chance to pull over...the engine would probably sustain engine damage if maintained at red line for a prolonged period but that would be better than an accident.
so the transmission would respond to shift to neutral under load.
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