Over the past 3 years I have owned and driven my Acura RL, commuting every day to work and even taking the car on long trips. During that time the CMBS feature has been enabled, but it seems to do so improperly. The following example happened shows how it the vehicle did not stop in a straight line, but caused the car to go into foliage.

On Thursday, November 24, 2011, I was driving my 2008 Acura RL. As I was about ten minutes away from my home, the vehicle in front of me suddenly braked. This resulted in my vehicle’s “Collision Mitigation Braking System” activating. The system only activated the brakes on the left front side, which resulted in my vehicle swerving in a rightward direction. The front left brakes did not activate. My vehicle ended up going into a center foliage area and then hitting a rock. This is not the first time the “Collision Mitigation Braking System” has been faulty in its activation. I have experienced the system activating on only one side before. The vehicle also did not fully brake properly previously. I was very scared last time.
This time, the vehicle has been damaged on the underside due to the rightward swerve and then the vehicle going into the foliage area.

I am curious if any other forum members have had similar issues and found a resolution. I am aware of that the issue has been taken to court and Honda did win, but maybe there are some other folks with better luck. Thanks for any input.

 

First off, if only the left side brakes clamped down the car would veer to the left. Think about it.

Secondly, in an emergency situation the CMBS brakes evenly to slow the car. It does not have the ability to distribute the braking power to one side or the other.

 

He meant "right front side".
Fixed.

OP, I am by no means an expert on brakes, but it is my understanding that the brake system is an all or nothing ordeal. You can't just get one corner to brake. It is a hydraulic setup that is attached to all four calipers. If the CMBS braking were to act in such a manner, so would your normal braking. My opinion is user error.

Do you have documentation of the class action suit?

EDIT: Nevermind. Here ya go Their claims and your claims are not related. They court dismissed the case on the ruling that the California laws violated did not cover all 47 jurisdictions that the class action members resided in.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CFAQ FjAA&url=http%3A%2F%2Fwww.ca9.uscourts.gov%2Fdatas tore%2Fopinions%2F2012%2F01%2F12%2F09-55376.pdf&ei=qdT6T_W4POa42wWd6ITXBg&usg=AFQjCNGyne 5o9lefyukhKai8rRLVxaUevw&sig2=nMQ7lMObsheS32AEuFJ4 DQ

 

The lawsuit was brought about by people that misunderstood how the system works. In its final stage the CMBS is designed to minimize damage. It does not completely stop you from colliding with the car in front of you.

 

You talkin' to me? Maybe you missed me linking and bolding the actual case ruling?


Well, that link didn't work. This one? http://www.google.com/url?sa=t&rct=j...fyMM9--zOMvOSw

 

The issue was the way Acura marketed and sold the CMBS system in its commercials and materials vs. the way the system worked in reality. The person who brought the suit was a member here - he didn't misunderstand how the system works, it didn't work as Acura advertised it.

 

Indeed. I remember the original Acura commercial. It depicted an RL 'seeing' through the fog and rain to detect a trailer stopped in the road ahead.

When in fact, the system shuts down in poor weather as not to create false target detection by the radar. That is the basis of the dispute.

Further the activation of the system was depicted in 3 progressive stages, when in reality those stages may overlap, in essence skipping a stage. That may confuse a driver who may have expectations as to how the system operates and will prompt the driver.

Not surprisingly, all the original RL commercials that depicted CMBS have disappeared and were removed from YouTube, etc.

 

Is bad weather detected through the radar targets?
I'm thinking a good noise suppression could work.

 

CMBS uses millimeter-wave radar technology. I do not know the frequency and cannot imagine anyone trying to modify it (if at all possible).

From the manual:

Driving your vehicle in bad
weather (rain, fog, snow, etc.)
will cause the system to shut down.

 

understood, but they must have some algorythm to detect multiple suspicious targets as the way to detect bad weather. I would think they could improve software to filter noise. Or are you saying milimeter-wave technology cannot "see" through rain, snow etc. and thus filter would be useless

 

The US Army Space and Missile Command has a paper that discusses the atmospheric impact on MMW technology. In section 2 there is mention of a program which has potential to address and correct atmospheric variations (noise) on MMW. Hopefully this will be available to consumer automobiles before warp drive (which may help this thread get back on topic). I personally, would be more interested in Deflector Sheilds.

http://www.nato-us.org/sensors2005/papers/mcmillan.pdf

When I bought my RL I read up on the limitations of CMBS. I also had false targets activate when I test drove a model with CMBS. I had no special need for ACC and I knew I certianly did not want PAX. I am still happy I decided to pass on the 2006 Tech Package.

 

Got it - thanks

 

Anyway, is there anyone here with enough understanding of brakes to confirm that the OPs situation is impossible, i.e. one caliper gripping without the rest during CMB while normal braking would be unaffected?

 

The OPs one-sided braking is only possible if VSA somehow activated OR there was a leak in half the braking system. The CMBS system applies brakes identically to stepping on the brake pedal, so if you think of how you can only have the caliper on one side activate while stepping on the brake pedal, these are it.

Not sure what exactly happened in the OP's situation, but my guess would have to be VSA intervention, because if it was a brake leak on one side, I'm sure the OP would have noticed continued lop-sided braking.

 

I can't claim to be a technical expert, but I have 45,000 very happy miles under my belt with CMBS. CMBS comes with system sensors for brake master cylinder and brake pressure at each wheel. If there is low pressure at any point the CMBS/ACC is disabled and you see a very annoying large warning light until it is resolved! I have recently had this issue with mine.

On the general point on the value of CMBS, I find it very reassuring. Glance in the rearview mirror just when the car in front brakes hard and you have those vital extra milliseconds response. The only false readings I get are when approaching a vehicle in the next lane on a gentle bend and occasionally it thinks the car in front is in my lane and I get the stage 1 response.

In England, CMBS/ACC also came bundled with Lane Keep Assist and the combined package makes for stress free long distance motoring

 

I would award inventor of CMBS with Nobel Prize. Best car feature I ever experienced. It just perfect!

 

Thanks for all of your input. It seems my vehicle is acting differently than others since all four brakes are slowing down the vehicle for other posters as opposed to just one side on

Below are two photos of the actual incident



And below is a larger image of the damage.

http://www.dumpyourphoto.com/photo/view/123639/dw6sjbih

The damage has since been fixed (By Western Auto Body In Torrance CA). I'm not sure what to do as far as getting the CMBS inspected. The Acura Dealer closest to me has had my car for a week since the last incident and are saying that nothing can be found. Any suggestions?

 

Thanks. I meant leftwards. The CMBS does not apply brakes to all four of the wheels. The steering wheel turns leftwards forcefully out of my hands.

 

Are you sure there was not a rut in the road that would have caused the left swerve? I still don't see how the CMBS can apply the brakes any differently than you just pressing on the pedal. That's all it does once it decides that it needs to brake.

If you want to experiment, just test it with the ACC. The ACC mechanism uses the SAME functionality as the CMBS to apply brakes to the car! Just set your ACC on any city street and wait till you come upon a red light (with a car in front of you!) and feel the car apply the brakes. It should be just as if you are stepping on the pedal. See if you get a swerve when that happens.

 

I have some felling, that problem is not CMBS, but it is either glitch in ABS or mechanical fault with breaking system, may be even hydraulics. But ABS more likely, as there is obviously something wrong with breaking force distribution. I would definitely insist on comprehensive inspection on all systems involved in breaking process.

 

The CMBS service manual states this: The CMBS is activated via the ACC and the VSA systems. There is still no mention of how one brake could possibly be applied more than another, but if it did indeed happen, I would guess that the VSA system malfunctioned. Good luck. There are quite a few systems that need to work in parallel to make this system work, and unfortunately for your wallet, only a dealer would have the best chance at figuring it out. Keep us updated on the results.

It may be worth turning the system off for a while and back on. There are quite a few DTCs that correspond to the CMBS system, and most result in an ACC replacement if the problem is real.

 

It seems kind of dangerous to be testing the ACC on a public road since I think the CMBS is already glitchy. Though, it is a good suggestion. Maybe I can try to reproduce it in a parking lot following another vehicle.

As far as the "rut in the road," I had a chance to review the road coming down the hill where the accident occurred. I drive that road twice daily and did not see anything. I also took some pictures. The "left swerve" has happened on two separate occasions making me thing it is a car issue.

 

I will try turning off the system and restarting it. The RL was at the dealer for a while for an inspection the past week for the issue but they didn't find any problems. If i find anything else, I'll post it.

 

Yes, it could be kind of dangerous, but just have ACC set to the farthest following distance and then get ready to apply the brakes yourself with your foot above the pedal. You can't really test it in a parking lot because I believe ACC deactivates below 25MPH. Also, the faster you are going, the farther the distance before activation. I've done this test many times at highway speeds as well as in the city. I've always liked to test to make sure my millimeter wave radar and auto braking works... so this is how I did it. It's amazing how the computer can brake hard and smooth at such a constant progessive rate.

It's hard to describe in writing, but it's not too hard to do and will tell you for sure if your CMBS is the problem. As I said before, I still think it's VSA because CMBS just applies the brakes as if you stepped on the pedal.

 

Ok... I just tested this again on my own car using ACC, and SCRATCH WHAT I SAID about setting ACC and coming up to a car stopped at a red light. The brakes activate way too late in that situation and is actually scary!

The BETTER way to do it is to set ACC and come upon a MOVING car like going downhill or something. When the car in front brakes, your ACC will brake and you will see it activate well before it gets scary close. If the car slows to below 25 MPH though, get ready to brake yourself because ACC will turn off even if it is in mid-braking when it drops below around 25. In any case, this test method is easy to pull off every time and it works much better!