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An Engineer’s Eureka Moment With a G.M. Flaw (nytimes.com)
43 points by wallflower on March 29, 2014 | hide | past | favorite | 38 comments


that an unsuspecting driver could bump the ignition key and cause the car to cut off engine power and deactivate its air bags.

I didn't know that turning off the ignition would deactivate the air bags. I've welded on vehicles before, and have talked to body work guys about it. Everyone says to disconnect the battery so you don't accidentally set off the air bags. It can happen by stabbing the mig wire into the air bag harness, or just by letting the welding lead lay next to it and inductively causing current to flow.

Seems like if you're parked in a parking spot, and someone smashes into you hard enough that the acceleration can trigger the airbags, you would want the airbags to go off. I don't know why you would ever want to disable the airbags (except baby in car seat).


The airbag sensors require power, and would, perhaps only eventually, drain the battery. I use a bluetooth adapter on my OBDII port and I suspect this very small device drained my battery after a couple weeks of not using the car. It would be unacceptable for cars to come off the production line that way.


The ADXL78 series [1] which is recommended for vehicle collision sensing draws 1.3 mA. If it were the only load, it would take on the order of ten years to discharge a car battery, which is well below the self-discharge limitations. I don't know if lower power sensors are available, or if some rule like "enabled for 24 hours after the car is run" would be appropriate, but lack of power for the sensor does not seem like a good reason for the airbags to be disabled.

Bluetooth devices actively searching for devices to pair with could plausibly draw significantly more power than that.

[1] http://www.analog.com/static/imported-files/data_sheets/ADXL...


> if some rule like "enabled for 24 hours after the car is run" would be appropriate

There are pressure sensors, such as those used to determine if the passenger airbag should be enabled/disabled. That should be the reference for both driver and passenger; if seat = occupied, trigger airbag if collision detected, regardless of engine status, ignition switch position, etc

If only automakers could update this sort of logic over the air...


I don't think any car lasts more than a couple of weeks without being turned on, OBDII bluetooth dongle or not

For the airbag I think the sensors are passive, but even if they aren't, a grace period could be added (like, it will shut down after someone shuts off the car, then opens and closes the door)


You have a problem if yours does not.


Often, the problem can be summed up as "Canada is below zero for months at a time."


Electric arc welding can fry the electrics (think ECU etc) on a vehicle if you don't disconnect the battery. Airbags would be at the lower end of your concerns.


It's actually better to disconnect the ECU entirely if you can. There is a large wiring harness that brings 40+ wires together into one or a couple of plugs which you can undo in a few seconds.

Plenty of ECUs have been ruined by folks getting their exhaust welded when the people doing the welding don't really know what they're doing. Especially if they normally work on older cars which tend not to have sensitive electronics.


It's kind of funny that now that everything in a car is effectively software-controlled something like a mechanical ignition switch is still left to control a main circuit that's so crucial it will stop the engine if broken. To think, we do have wireless car keys already, with just a start/stop button on the instruction panel.

Even with physical keys I would assume that this particular circuit would be controlled via a relay and the car computer would only let the driver to stop the engine by removing the key if the car was not moving.


It really depends on the car.

My car, for example, is a Chrysler 300 and there is no real connection between the key and what provides power to the engine.

Here[1] is a diagram showing how the CAN bus works on the Chrysler/Dodge LX platform vehicles. The SCM/SKREEM module on that diagram is where the ignition switch and logic that talks to the keyfob is and makes sure you have a valid key. Here's a recall related to the module which hints a little bit about what it is and does[3]. Note on the recall that this applies to a whole bunch of Dodge/Chrysler platforms.

Based on the wiring diagram[2] (for Dodge trucks, which is one of the platforms that [3] applies to), the SCM/SKREEM (called Node-Wireless Ignition in one diagram and WCM in another) uses a 2-wire CAN bus for its communication. Once the SCM/SKREEM validates the key it sends a message on the CAN bus to the engine controller to tell it to start the engine.

In these vehicles, whether the engine is on or off is purely under software control. That said, I'm not going to try turning my car off while I'm driving.

[1] http://the8thlayerof.net/2013/11/10/canbus-vehicle-network-d...

[2] http://tucrrc.utulsa.edu/DodgeCAN.html

[3] http://project-jk.com/images/tsb/TSB_08-007-08.pdf


Given how Toyota has had the opposite problem, I would not be comfortable if the engine could not be stopped in this manner.


In the news over the last couple of years, I've seen more than one report of schoolchildren stopping a runaway school bus (driver passed out, etc.) by turning off the ignition key. So this behavior can be a feature, not a bug.


Turning off the engine doesn't have to be attached to the mechanical ignition switch.

There are already cars where the ignition switch is completely wireless and software-controlled. For example, many cars offer a start-stop feature which turns the engine off when standing in red lights and automatically starting it again the foot moves from brake pedal to the accelerator. People are going to learn that there's no such thing as ignition switch anymore.

Motorcycles have red kill switches that shut down the engine completely. A school bus or a car could have something like that.


"In one deposition, Mr. Cooper confronted Raymond DeGiorgio, the head switch engineer on the Cobalt, with the differences between the original switch and the replacement. While Mr. DeGiorgio said he saw the differences, he could not explain why the part had been changed without a corresponding change in its identification number."

Since the part was changed on the later models (post '06-'07) without changing the part number, that means there is no way to tell the new ones from the old defective ones. This goes against commonsense, why was this done?


This goes against commonsense, why was this done?

Others have speculated it was done for liability reasons, that's IMO the most likely explanation. The beauty of civil litigation is there's an easily accessible paper trail. It would be interesting to see whether or not GM has a habit of changing designs without changing part numbers.

However, frequently designs get changed by "marketing" without a part number change, even in situations without possible liability. E.g. wireless routers are sometimes totally revised while retaining the same part number. Apple also likes to implement stealth changes.

Most engineers understand "commonsense", most marketing pukes don't.


It seems like either they thought the change was insignificant, or they were trying to hide the fact that it was defective.


This goes against commonsense, why was this done?

Almost certainly because they knew about their own enormous liability. They settled with a family for this issue in February of 2006, and not long after did the engineering change, albeit leaving the defect out there on millions of cars (insert Fight Club quote).

I suspect this issue is going to continue to grow until someone is charged with criminal negligence causing death.


> I suspect this issue is going to continue to grow until someone is charged with criminal negligence causing death.

Which is worth noting won't happen; not under this administration with Holter behind DOJ's steers. Keep in mind, GM was bailed out and saved from bankruptcy by taxpayers money, despite their uproar. Clearly, GM is in bed with administration.


I am not saying this is the drivers fault as, based on how the facts are presented here, is clearly GMs.

But- Are the deaths due to the drivers not adapting quickly enough to the loss of power steering? After all breaks and steer are still working?

I have driven a vehicle without power steering and it wasn't that bad, and the vehicles in question (Cobalts) are rather light.


Power brakes will disappear when the built up vacuum runs out, and one could easily exhaust it when panicking. Driving without power steering on my 2000lb Civic is actually quite fun (except in parking spots), and at highway speeds lack of it isn't really even noticeable. On the other hand rolling my car down a driveway, starting to stop, and then having the power brakes suddenly run out always startles me, even at that low speed.

I think a lot of these accidents are indeed caused by drivers panicking from being completely out of touch with what the car is doing, but that does not mean there is a straightforward solution. Knowing what a failure of power steering/brakes feels like, I'd just coast over to the breakdown lane and stop with the hand brake/engine. On the other hand, I once had a passenger (in my old automatic transmission car) accidentally bump it into neutral when I was on the highway and it took me ten seconds to figure out what was going on.


A power steering rack & pinion is rather different than a manual rack & pinion. In my experience when a car loses power steering it's a real pain. Especially if you're used to power steering. Having it drop out could feel like the steering wheel has locked up.


Keep in mind, it's not just that the power is getting cut, it's getting cut because the key is getting bumped or otherwise turned to the off position. Of course, there are generally 2 different off positions, and in one of them (the really off position), the steering wheel also locks. So yeah, losing power steering, power brakes, the ability to accelerate, and possibly even having the steering wheel locked up, all while the car is in gear, can make it impossible to avoid collisions. Combine that with the fact that it is a completely sudden surprise to both the driver and anyone else around the car, and to top it off, the airbags are disabled. It's generally an extremely dangerous situation.


"Due" and "because of" are very difficult questions. Someone whose family member died but who has a bigger beef might well conclude, "because he didn't get the bonus that [some company] owed him, he ended up having to settle for a Chevy Cobalt - a car that likely ended up killing him."

Is this use of "because" correct? Sure, why not. He wouldn't have died if his bonus had been paid? Might well be true.

I would personally not be interested in "due to" and "because of". To answer your question, you could have asked instead,

"I wonder if experienced drivers who were used to driving without power steering would have not been adversely affected."

Note: my example is a case where blaming a lack of bonus on the death is clearly wrong - but isn't attributing causative power to someone not being used to a car suddenly changing into a totally different input paradigm equally wrong? Better to stick to the factual question for starters.


The article stated that you also lose airbags when the ignition is not in the run position. That seems pretty significant!


I think that this is the key argument fir the deaths caused. But, I was under the impression that the effectiveness of air bags compared to their hazards was coming into question in testing anyway. a seat belt saves many more lives than an airbag?


The combination is the best (apart from not crashing at all). I had heard that US airbags were bigger than European ones as they were designed to attempt to compensate for the lack of seat belt use (which was apparently common in the 90's).


I was wondering the same thing. As a teen I drove a small car, and at least once or twice while playing around with shifting gears (mind you, this was an automatic) I accidentally shifted into reverse while in motion, causing everything in the car, including the engine and power steering to shut down. All I did was quickly turn the ignition key to restart the engine and all was well.

Yes power steering loss makes the car very sluggish, but really you're just coasting at that point and turning the ignition switch quickly is second nature. I'm sure it could be a little more frantic at highway speeds.

I wonder if this is something that should be taught in driver's ed?

(Regardless of my above comments, I do agree GM is responsible for sweeping this under the rug)


Steering as long as you are moving isn't too bad. With brakes, you've generally got one solid push of the pedal (vacuum reserve in the booster) before you have to stomp VERY hard to get a vehicle to stop.


I had this happen to me years ago while driving on an isolated stretch of highway with no streetlights or other ambient light. Suddenly the engine cut off and it was completely dark while rolling down the highway. Needless to say, it scared the hell out of me.

Fortunately the road was straight and after about 3 second it came back on as I was trying to see where the edge of the road was, and no other cars were around (although that would probably have helped me see or regain perspective).

It's easy to imagine how I could have rolled off into a ravine regardless if I could forcibly steer the car.


Directly cause deaths? Maybe, maybe not, I guess it depends how far into a root cause analysis you go.

Regardless, while driving without power steering and brakes is possible when you're expecting it, it's quite a shock when you aren't. Especially if you've never done it before, which I suspect is true for many of today's drivers.

I can easily envision circumstances where loss of power could cause an accident. Fast road, sharp corner, surrounded by woods, etc.


I concur, as a driver you're probably more likely to bump your key when turning which could be especially bad in some areas/speeds/locations.


Can we stop posting links to nytimes until they get rid of the paywall?


NYTimes is often the best or original source for an important story.

Most readers here can either afford a subscription, or know how to read a story-of-interest without sending paywall-triggering cookies.

Some great reporting entities, using information beyond that which we have as readers, have decided such leaky paywalls are better than the alternatives. Against that domain expertise, we don't need HN to adopt some uniform, ideological "boycott all paywalls" policy. If it's so easy to get the same good stories from elsewhere, find them and submit them.


Don't you think it's worth paying for good content?


You can read it in an incognito/private window.


Just Google the article to bypass the paywall.


Funnly, the paywall did not appear on my iPad.




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