My Leaf roll back and almost kill a kid!

It happens to my wife once but I didn't believe her last month. I've ask her what happen and describe in sequences. She told me had her foot on brake, press start then put it in Reverse while the foot still on the brake from the beginning. Once in Reverse she looks back and saw people coming so she kept her foot on the brake. All of sudden the brake just felt soft and sink to the floor and car roll. She panic and lift her foot half way off the brake and press again it still roll; while the parents walking in back screaming. My wife pulls the electronic brake it didn’t work. Finally she lifts her foot of the brake completely. Somehow the software figures out the reference point and she hit the brake and it stop. The parent came screaming at her trying killing her kid. After that experience she didn’t borrow my car anymore. So I just brush it off but pay attention to my Leaf thinking she must have done something wrong. Last night first time experience her same symptom. I had my foot on the brake press Start Button then put the car in Reverse and the car roll while my foot is still on the brake. The brake just sinks straight to the floor. I quickly lift my foot completely off the brake and slam on it and it stop. I fear one day someone going kill somebody while the car in Reverse driving a Leaf. I fear during the start the brake lost it reference and software doesn’t know where the reference point begin.


Other Problem!
-Car park on uneven pavement car brake lock! Therefore when you press brake your car can’t start. It can’t register my foot on the brake. (Solution I observe pulls my emergency parking brake on; wait then foot brake release. Turn off the screen now press your foot brake and feel it depress car register your foot on brake then it let you start. Nissan need fix software if roll and lock on an uneven pavement. Lock the brake fine but activate the parking brake then release the foot brake that lock. User now press brake again then start..problem fix! If Nissan not paying to this issue not many Leaf owners will pull their parking brake therefore the system kept saying press brake to start. The only way to release this brake pedal lock you have to activate the parking brake manually. Nissan software should do this automatic!
Otherwise this car is awesome! I’m not sure how long they are keeping my car but once I get it back I will do my best to update everyone in the forum. I just feel my duties to report for safety of Leaf owner to get this fix and enjoyable for future Leaf buyer!

12/01/2012

Ok got the call today to pick up my car tomorrow. Their explanation was I got all these faulty errors was due to a 12V battery. They have all my error codes download and conclude the 12V cause the can bus to go hay wire. They replaced the 12V battery and drain my main battery and recharge. They said everything is working fine. I’ve ask them over the phone was there any cause from the mechanical brake. Their respond was 12V cause faulty error and no mechanical brake issue.

Also the 12V will solve the start issue on the uneven pavement. Guys don’t worry once I get my car back I know where to park to see if this problem is resolve.

For the record before I brought my car in for service. I did check the 12V battery every time I had issues in past. I measure with my voltmeter reading 10.7V to 11.2V.

Anyway I will continue to monitor my issues and update in 3 months. If I see no more issues; I can conclude the 12V battery replacement fix all my issues. I will also ask if they updated the software or kept the current version.

Again Thanks to all that supported my issues and wanting Nissan to improve for future generation to enjoy the Leaf and safety come first!

12/02/2012
Pick up the car this morning. Once started the Leaf mileage reading show 105 miles on display. I’ve notice the brake felt different in a way that it felt stronger not relax feel as before. I drove the car home and measure the voltage and new battery reading 12.31 volts. Anyway I will do more testing on uneven pavement testing in next few days. Hope all my problem is resolve due to low 12V battery. If this is case we should all measure our 12V battery often….wow! Now I’m wondering what happen in real situation when the car let you start up and while driving the 12Volts battery is lost…does this mean you lost power to certain controls? I just hope we don’t lost power to our emergency brake…

"Report came back found multiple codes 62 total. The mechanic in charge called the Nissan Tech Line and had them review all but found all up to date. Tech Line confirms that 12V battery went low; recommendations from tech line replace new 12V battery (NB51R). Test drove and check for codes again. All to be ok".

12/03/2012

ok measure with another voltmeter at work. The new reading is 12.47volts. This battery is brand new; replacement just 2 days ago.

Also had a chance to park at 3 different locations on uneven pavement. I couldn't repeat the brake lock symptom anymore.

So I'm going to conclude all my problems that I have listed is due to the 12Volts battery running low in range of 10.7 to 11.3 volts. I hope in near future someone post issues relating to car error. Ask them check the 12volts battery.

Also I agree with one of the post that Nissan should send an email or letter or warning that our 12volts is below the requirement level. I though Nissan download our car information when we hit agreement for information download or I'm mistaking that information download each time we start the car is tracking milage?

Anyway if Nissan can manage to measure the 12volts an display "Warning 12 volts battery replacement or check". It can save lots of headache for future Nissan Leaf owner!
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After thinking with all the pain I had to put up with in past few months. I realize get rid of the tree display and offer me a display to monitor the 12 Volts battery level!!!!!!!!!

We all agree the 12volts battery is the main component in the EV car( I consider the 12volts is a Heart like human body; Heart stop brain won't function anyway)! If 12volts low or dead many of the operation will be non functional! Can someone let Nissan know give us a 12volts display scale! Otherwise future Leaf owner got go buy a voltmeter. When Nissan can display it on the screen.

VIN #000936
Milage:23,700

Well, that seems to be something not previously reported. Good that no one was injured.

Trust you have arranged to have a Nissan shop look into those unusual happenings.

That's pretty scary! It's good no one was hurt or killed.

There is new firmware available for the braking system in the LEAF which addresses the brakes being grabby. I wonder if it also addresses this issue.

In any case, I would definitely get the car in to your Nissan dealer as soon as possible.

I tought the pedal connection to the brakes was mechanical with hydraulic assist. With that in mind it is strange that flooring the brake wasn't enough to stop the car.

vegastar said:

I tought the pedal connection to the brakes was mechanical with hydraulic assist. With that in mind it is strange that flooring the brake wasn't enough to stop the car.

Click to expand...

That was my first thought, as well. But after thinking about it further, the brakes on the LEAF are assisted by an electric pump, so it seems possible that a failure to start the assist pump motor might result in such a fault. Perhaps fluid can flow backwards through the pump if it is not running.

In any case, the assist does not come directly from the running engine as it does in a conventional ICE, so it is certainly possible to have the car drivable but the brake assist off.

I have no idea why the parking brake was also not working. Perhaps the ultracapacitor got into a discharged state somehow?

The LEAF uses a fairly standard hydraulic braking system just like any other car, with the main difference being that the brake boost is done via electromagnetic coils instead of a vacuum and diaphragm (because there's no engine intake manifold to provide a vacuum). The strength of the boost is what gets controlled to balance regen and friction braking.

If the boost system fails you should still have brakes, but you would have to push very hard on the pedal to get strong braking force - they will feel very stiff, not soft. Under no circumstances should the pedal go all the way to the floor. This is a serious mechanical malfunction of the braking system and you should have it looked at immediately if not sooner. I guarantee this has nothing to do with firmware.

My two cents. Also, the electric parking brake should have more than enough schlitz to stop the car, especially if you pull it twice to "double engage" it. The capacitor has nothing to do with the parking brake AFAIK. It's there to maintain the ABS and hydraulic boost systems.

Edit: reading the service manual more carefully, there appears to be a small, physical gap between the pin attached to the brake pedal and the master cylinder internals. It's the movement of the pedal within this gap that allows regen with no friction braking at all... but that's irrelevant here since the pedal was fully depressed. You should have full mechanical braking at that point, and the fact that it still failed means it's a mechanical failure.
=Smidge=

If the boost system fails you should still have brakes, but you would have to push very hard on the pedal to get strong braking force - they will feel very stiff, not soft. Under no circumstances should the pedal go all the way to the floor. This is a serious mechanical malfunction of the braking system and you should have it looked at immediately if not sooner. I guarantee this has nothing to do with firmware.

I agree with Smidge. This is a mechanical problem and needs to be looked at NOW.

Now that we are aware that it can happen we should all be ready to push the park button in an emergency like this.

I also have warned my wife that if the power steering fails....The steering is probably going to feel like its locked...but to hang on and use lots of muscle. It could catch you off guard in a corner

Smidge204 said:

Also, the electric parking brake should have more than enough schlitz to stop the car, especially if you pull it twice to "double engage" it. The capacitor has nothing to do with the parking brake AFAIK. It's there to maintain the ABS and hydraulic boost systems.

Click to expand...

O.K. Agreed that it looks like the ultracapacitor does not provide backup power to the parking brake. IMO, this is a major defect in the system design since loss of 12V power means loss of the parking (emergency) brake. Perhaps this is one reason they chose to move back to a mechanical brake in 2013. It IS mechanical for 2013, is it not?

In this case, maybe the issue was simply that the emergency brake was too slow to provide help in stopping the car in time. OTOH, it appears there were serious problems going on, so perhaps power was lost to the emergency brake system.

69800 said:

Now that we are aware that it can happen we should all be ready to push the park button in an emergency like this.

Click to expand...

Yes, I was starting to think about what to do in this case and shifting to park came to mind. Does anyone know the maximum speed at which the parking pawl will move into the locked position?

when i first read your post, i was horrified that this scenario was even possible.

I have spent quite a while in my driveway (very steep) trying to reproduce this and have failed.

my driveway is so steep that in Eco, it will roll backwards if there is no foot on Accelerator or brake. in every instance, it was very easy to stop the car (i do it several times a day now. i live on street that is one block long and there are kids playing on it ALL the time)

have to guess your wife was simply not pushing on the brakes very hard. I was able to get the brakes to lose their sponginess and it does seem like you need to push somewhat harder to brake??

during this trial, i also noticed a very slight change in my mechanics. unlike forward momentum which pushes you into the brake direction when slowing, reverse pulls you away from it and there was a few times i had to be diligent about simply not pushing "harder" but pushing "farther"

i will say one thing. i am at 1.8 miles/kwh after .3 miles of driving...not a good start to the day!

either way, i think you should try to reproduce this. if you cant? well...but there is always the possibility of a defect no matter what anyone tells you here. we can only relate our experiences with our cars. keep in mind; i have ZERO experience with yours

I would take it in and get a new master cylinder installed along with full flush of the fluid. Unless Nissan can duplicate the issue and it is known to be something else. This should be under warranty.

The parking brake does take a couple seconds to engage.... and could seem like an eternity during a panic. In all the confusion I think this may have been what stopped the car.

I had a loose bleeder valve on my saturn once. It acted just like this. Tightened the valve and fixed the problem. Had to rebleed though.

The parking (emergency brake) and the regular four wheel discs are completely different systems. There is NO WAY both failed at the same instant, and then magically otherwise work.

A dozen computers and that cannot be detected?

Guessing it's design error, software issues or driver error

Will the emergency brake engage while the car is moving?

Philip

philipscoggins said:

Will the emergency brake engage while the car is moving?

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Yes. I think they even mention using it it motion in the owner's manual.

Edit: I found the reference in the manual:

2011 LEAF Owner's Manual Revised said:

- If the electric parking brake must be applied while driving in an emergency, pull up and hold the electric parking brake switch. When you release the parking brake switch, the parking brake will be released.

Click to expand...

RegGuheert said:

philipscoggins said:

Will the emergency brake engage while the car is moving?

Click to expand...

Yes. I think they even mention using it it motion in the owner's manual.

Click to expand...

see this quote

http://www.mynissanleaf.com/viewtopic.php?p=235516#p235516" onclick="window.open(this.href);return false;

he has another post where he details this test, but I could not find it.

palmermd said:

see this quote

http://www.mynissanleaf.com/viewtopic.php?p=235516#p235516" onclick="window.open(this.href);return false;

he has another post where he details this test, but I could not find it.

Click to expand...

So it seems there may be two behaviors:

1) Below a certain speed, the parking brake will engage and remain engaged until the accelerator pedal is depressed.

2) Above a certain speed you must hold the lever up to get it to brake the car.

RegGuheert said:

palmermd said:

see this quote

http://www.mynissanleaf.com/viewtopic.php?p=235516#p235516" onclick="window.open(this.href);return false;

he has another post where he details this test, but I could not find it.

Click to expand...

So it seems there may be two behaviors:

1) Below a certain speed, the parking brake will engage and remain engaged until the accelerator pedal is depressed.

2) Above a certain speed you must hold the lever up to get it to brake the car.

Click to expand...

I don't believe that holding it had any effect. It released when at speed, but like I said I could not find the original post where he details the test. Was posted in Spring/Summer of 2011. Hard to search that far back.

edit: I found it. http://www.mynissanleaf.com/viewtopic.php?p=66057#p66057" onclick="window.open(this.href);return false;
if you look at his followup post, yes you can engage the brake by holding it even if you are at speed.

RegGuheert said:

palmermd said:

see this quote

http://www.mynissanleaf.com/viewtopic.php?p=235516#p235516" onclick="window.open(this.href);return false;

he has another post where he details this test, but I could not find it.

Click to expand...

So it seems there may be two behaviors:

1) Below a certain speed, the parking brake will engage and remain engaged until the accelerator pedal is depressed.

2) Above a certain speed you must hold the lever up to get it to brake the car.

Click to expand...

This is my experience. Although I have never held the lever up... but IIRC it did fail to engage with a tap at low speed along with some warning lights.

Just call me a bit "over-skeptical": OP's first post, strange grammar; hard to believe description of a problem????? I take his post with a grain of salt. :? :?