Scary reduced brake power / pedal feel

After turning the car on the brake pedal respons / feeling is different and the brakes starts braking only when the pedal is pressed at least 1/2 inch deeper then normal. The braking force is way less then normal at the same pedal pressure and there is no regen with brake pedal. (4 bars SOC, but happens at any SOC) Feels scary and unreliable. No warning lights or any indication!
Turning the car off and 10 seconds later on again does not make a difference. Leaving the car off for 30 minutes or more and this issue is gone again. It also comes at random, but never in the middle of a ride. When it's there, it's always direct from the start / turning on.
It started this summer july 2014 and happend at first about once a month, but now, at least, once a week.

relevant DTC codes are:

BRAKE C1A62 CONTROL MODULE POWER SUPPLY (part number 46007-3NA0A )
BRAKE U1511 POWER SUPPLY BACKUP UNIT COMM (part number 46007-3NA0A )

This Monday I will take the car to the dealer and post here what they have done about it.

Just for our information, how old is this Leaf? Which model year?

It doesn't sound like this is the problem, but have you ever driven a car with a bad master cylinder? If you have a bad master cylinder, the pedal will go all of the way to the floor with no effect if you press gently, but if you pump the pedal, you can get it to brake normally. But if you had a bad master cylinder, regen would still work. Your symptoms are very different.

Bob

Check your 12-volt battery. Both of those error codes are related to power supply.

Gerry

Thanks for your fast response.

It's a 2012, with 16000KM (10000miles).

At the dealer, I will tell them to check the 12v battery. But wouldn't it be strange that in case of 12v battery wear, the brakes are the first part of the car that stops functioning well?

EV1 said:

At the dealer, I will tell them to check the 12v battery. But wouldn't it be strange that in case of 12v battery wear, the brakes are the first part of the car that stops functioning well?

Click to expand...

It would be. In fact, it is!

Thank you RegGuheert for the link to that topic

Oscar had a lot more issues, but there are similarities. I just read the whole thread...
So this car has a HV 96x2 cell Li ion pack, balanced per cell, but does not know how to maintain a 12v lead-acid battery?

I did not mention it, until now, because it has nothing to do with the technical part of this problem, but my wife actually had a small accident because of this issue! The brakes did not react the first inch of travel of the pedal and when they did, the braking "power" was way less then normal. She "hit" another car at a parking lot, in front of her, with 2 or 3 KM/h, so not very much damage, but there 's a big superficial scratch.

The Nissan Leaf has had some serious brake problems from the 2011 MY, and I'm sad to see the newer models still have these problems. It has resulted in at least 2 documented crashes (based on reading the U.S. NHTSA safety reports) and likely numerous incidents that were not reported. Personally, as a 2011 Leaf owner I have experienced some scary malfunctions with the brakes several times. Finally three months ago I traded in my lemon for a Mitsubishi iMiev, and I have not experienced even one issue with it! It's a world of difference: The brakes are consistent and reliable, and the motor power is proportional to the pedal position. With the Leaf, I could accelerate and then release pressure on the pedal and it would continue to ramp up power - it felt pretty dangerous - but in my new car I back off the pedal and it backs off the power as expected, every time. The visibility is way better as well. I almost hit a pedestrian twice in the Leaf because of the big blind spot caused by the pillar at the worst possible location, it blocks the view of the street corner at intersections so I have to move my head from side to side. Some day, a pedestrian will be killed because of this. Yet Nissan continues to ignore the reports of the braking issue and the other defects, rather than working to fix them! What can we do to make them listen? People have already gotten injured because of their negligence - one of these days it will result in a fatality. As members of the Leaf forum, maybe we can collectively do something to make them listen - but what?

^^^
Did you file safety complaints w/NHTSA on your specific safety issues/defects?

As for A-pillars, where else can they be? We've had extensive discussion on this. But, if you feel they're truly an issue, file a complaint w/Nissan and NHTSA on them as well...

johnr said:

Yet Nissan continues to ignore the reports of the braking issue and the other defects, rather than working to fix them! What can we do to make them listen? People have already gotten injured because of their negligence - one of these days it will result in a fatality. As members of the Leaf forum, maybe we can collectively do something to make them listen - but what?

Click to expand...

Ignore? You should really get ALL owners of all vehicles ten years old or less to report all legitimate safety defects experienced by the driver (i.e. not user error) to both the automaker AND NHTSA, preferably after the automaker has had a chance to resolve the issue, where applicable/possible. This applies to all vehicles, not just the Leaf.

As for the A pillar i agree that it needs to be where it is in most cars

BUT
for this particular car i dont see the need for it to be that thick/wide it really hinders the view - its a lease vehicle, so im willing to work around it but it is a sore "eye" when i have to move around before i turn a corner and or lift my point of view to turn right (LHD)

As this thread is about the braking issue, I don't wish to hijack it to discuss the A pillar visibility. Suffice it to say that I have driven other new 2014 cars that have just as good drag coefficient as the Leaf that have excellent visibility. This is something that could be fixed with a little redesign. But those of us who can see this is a problem need to speak up, and maybe if enough voices are heard they will do something about it. I have kept silent way too long. I have finally written a report to NHTSA. If enough people send in reports on the same issue then it's more likely NHTSA will investigate, with the result that these problem in the Leaf would be resolved and it would be a safer vehicle.

Link: https://www-odi.nhtsa.dot.gov/ivoq/" onclick="window.open(this.href);return false;

Got my car back after 2 days and the mechanic said he cleaned and fastened some doubtfull chassis-connections. He wants me to report after some weeks or when the problem comes back.
He did not replace the 12v battery (yet), but said it was the second thing to do on the list he got from Nissan. (forgot to ask what the first thing was, but i guess to check faulty connections)
The other thing he did was update the VCM, but he had no details about that update.
It seems the brake pedal is now a bit "higher" in general, but I am not sure if I am imagining that or not.

Regarding the safety-concerns, I would not classify my case as a safety issue. The pedal is lower then normal and the braking curve in relation to the pedal pressure is different, but it takes 1 second max. to adapt, as one automaticly presses further / more firm when not enough braking.

thanks for your responses, I will report back, solved or not.

When you say chassis connections are you referring to grounding?

Hope they got you all sorted out.

Yes, the negative side of the 12v battery and the thick cable(s) that connect it to the metal parts of the car.
English is not my native language.

It wasn't a problem with your English, only that chassis connections could mean a few different things. Should someone (especially me) have this problem in the future, a search should reveal this thread and your possible solution!

Your English is much better than my Dutch (which I got to experience when I worked for Fokker).

I'm not really surprised that it might have been a grounding issue. It's an often overlooked issue, even on ICE vehicles, that cause a long list of headache inducing and wallet destroying problems.

In any vehicle, if the car starts doing stuff that isn't good and electricity might be involved then the first step is to check your grounding connections. Unfortunately, in most vehicles, there are A LOT of them and usually they are in hard to reach places.

One day, my brakes starting acting that way as well, but only when I first start the car (once driving, everything was fine, ignoring the normal brake issues). Pedal would feel different, brakes would make some noise, and the door locks weren't functioning properly.

Eventually, my vehicle's 12V battery died, and all these problems were traced back to a bad door sensor on the driver side.

So if you run into problems again, please check if see anything else which might not be functioning properly.

Well..
More then 2 months has passed and the issue did not return! Relative quickly solved, I would say. Bad grounding / chassis connection.
The 12v battery was NOT replaced.

Thanks all for the help and tips.

Hello All from Québec Canada!!

I'm glad we found this post. I don't know if this is exactly the same problem as you describe, but I think it's worth sharing... As of today, we are several 2014-2015 Leaf owners in Québec which has recently reported some momentarily braking system failure, which seems to occur mostly in cold temperature, (below -20c). One of the Leaf owner that had the problem was able to take a video while it happenned to share it with the others. I know it's in french, but listen until the end, you will see and hear what the problem looks like. Apparently the brake pedal has to be pushed at more than 50% of it course before you can finally feel the car slowing down. After you hear some "Toc" Toc", only then it will start to brake but lightly. So far, we are aware that at least 5 Leaf owners from Québec had this problem and they reported it to Nissan Canada. We are still all waiting and very, very anxious to hear from them. Of course no dealer was able to find the problem, saying it could be just a bad relay contact in this cold weather (!!!!!!!) This braking problem can be potentially VERY dangerous and I hope Nissan will react very quickly before anything bad happens. Again, this seems to be happening only to 2014-2015 Leaf owners. I hope you will be able to see the video with this link.

https://www.dropbox.com/s/0rpjac5zo0yz5m8/Freins_leaf.mp4?dl=0&cid=1420776254730-996" onclick="window.open(this.href);return false;

This Saturday my 2015 SL with ~10K miles on it had the exact same thing happen. This was in the Palm Springs area and was not a cold weather issue.

It was very scary !!! Started the car normally with the brake depressed. Shifted into reverse and without removing my foot from the brake the car started moving backward. Thank God no one was behind me in the parking lot. After I regained my wits, and realizing I was potentially going to hit cars behind me, I slammed down on the brake pedal. This did finally stop the car. There was a tapping sound and a very bad grinding or groaning sound.

Anyway, being as it is here, my parking spot was immediately taken. I had to drive around the parking lot, extreemly slowly, trying to figure out what had happened and find another parking spot. I tried turning the Leaf off then on again several times. The problem still persisted. Each time I tied to brake, while driving around to find my new parking spot, the pedal had to be depressed at least 50%. There was a strange action to the brake pedal too. The tapping would start then the groaning/grinding sound from the motor compartment area of the car.

This was extreemly scary!

So once the car was parked I called AAA and had the car towed to the dealership in La Quinta, CA.

BTW, the problem was still there after at least 30 minutes waiting for the tow truck and once it was offloaded at the dealership Saturday evening after the service department had closed.

I will report once I have news from the dealership tomorrow morning (Monday 3/2/2015).

At least the Leaf is still under warranty! But this event has shaken my faith in the car's safety.

Franck0035... Thank you for the video! I couldn't understand the French, but that is exactly the tapping grinding/groaning noise my Leaf made Saturday!

At least if the problem has gone away Monday morning when I go to the dealership I can play the video for them.

Thank you so very much!

Franck0035 said:

Hello All from Québec Canada!!

I'm glad we found this post. I don't know if this is exactly the same problem as you describe, but I think it's worth sharing... As of today, we are several 2014-2015 Leaf owners in Québec which has recently reported some momentarily braking system failure, which seems to occur mostly in cold temperature, (below -20c). One of the Leaf owner that had the problem was able to take a video while it happenned to share it with the others. I know it's in french, but listen until the end, you will see and hear what the problem looks like. Apparently the brake pedal has to be pushed at more than 50% of it course before you can finally feel the car slowing down. After you hear some "Toc" Toc", only then it will start to brake but lightly. So far, we are aware that at least 5 Leaf owners from Québec had this problem and they reported it to Nissan Canada. We are still all waiting and very, very anxious to hear from them. Of course no dealer was able to find the problem, saying it could be just a bad relay contact in this cold weather (!!!!!!!) This braking problem can be potentially VERY dangerous and I hope Nissan will react very quickly before anything bad happens. Again, this seems to be happening only to 2014-2015 Leaf owners. I hope you will be able to see the video with this link.

https://www.dropbox.com/s/0rpjac5zo0yz5m8/Freins_leaf.mp4?dl=0&cid=1420776254730-996" onclick="window.open(this.href);return false;

Click to expand...

It's probably better to upload a better quality version to YouTube and it would be really nice if someone redid or dubbed English on top of it.

I can't understand a word of French and w/o having driven the problem (?) cars and other Leafs in comparable weather, I can't really comment on the behavior you're reporting.

However, the "Toc" "Toc" sound doesn't seem that different than other cars I've driven with ABS in snowy/icy conditions. Sounds like the ABS properly engaging and disengaging to me, while under a hard braking application.