NTB-12-086: Touchy Brake Fix Released. 2012 MY Fix Available

[TomT]

It continued to be much better today and I had a great drive of the type that normally makes it show up in spades...

Got mine done this morning and, so far, it is much better.

 

[RegGuheert]

It continued to be much better today and I had a great drive of the type that normally makes it show up in spades...

Thanks for the update! It sounds like they may have really fixed the problem.

Hope your issues are fixed quickly...

Me, too.

Thanks, guys! I'll let you know what transpires next seek.

Thanks for the heads up... I think I will wait.

That's probably the best thing to do.

What went wrong?

I'm not sure. Basically the reprogramming didn't work properly so now the car shows a red triangle for brakes. It basically has nothing other than unassisted manual brakes. No boost. No ABS. I'm not sure about B-pedal regen, but I'll guess that doesn't work either. I imagine the car would be pretty difficult to stop in this condition. The dealership sits on top of a steep hill, so I do not think they will take it on a test drive until it is fixed.

The service advisor came out of the service bay and said "You know that problem with your brakes you were complaining about when you came in? Well, they're not grabby anymore! Now when you push the pedal, it just keeps rolling!" :lol: This guy is a cut-up, so I thought he was pulling my leg. It took him a few minutes to convince me I really DID need to get my insurance card and go inside to get a free rental.

These kinds of reports make me leery about "fixing" stuff that isn't really broken, just mildly annoying.

Well, since it's on Nissan's nickel, I'm not overly concerned. Yes, the grabby brakes were mostly annoying, but I can imagine someone eventually spilling a drink all over the car because of this issue, which could be more than just an annoyance.

I do expect to have better brakes when I get the car back from Nissan.

I was thinking this would be a massively expensive repair for them based on previously-posted prices for the brake controller assembly:

Part MSRP Online Price
MASTER CYLINDER BRAKE CONTROLLER ASSY; Leaf 3778 2758

But I looked online and it seems that part has come WAY down:
MASTER CYLINDER BRAKE CONTROLLER ASSY; Leaf $1,906.57 $1,391.80

Hey, maybe I'll get new brake fluid out of the deal!

 

[DaveinOlyWA]

Aaron the LEAF Tech in Seattle states he has updated over a dozen LEAFs without a hitch so guess just a fluke of bad karma or something.

he says it highly unlikely to be tech error as its pretty straight forward procedure. he also says he has already had feedback from a few who says the problem did go away.

i spent about a half the day yesterday trying to reproduce it for SO (its our "date" day so we basically drove around nearly all day doing lunch, errands, projects, etc) and could not get the brake issue to work

**edit** Aaron has link to this post should be able to respond directly to comments. but just HAD to pass this along

i dont know what the loaner policy is for service but since you have a service contract it shouldn't be a problem. I am also here every saturday if you want to come

http://www.facebook.com/groups/seattlenissanleaf/permalink/478867042144738/?comment_id=480053952026047&offset=0&total_comments=34" onclick="window.open(this.href);return false;

 

[TomT]

My guess is that something disrupted the flashing mid-progress and resulted in corrupted firmware. It could have been a power glitch, data glitch or something else. It is rare but not unheard of when updating firmware. Usually there is a graceful recover process built-in, but it can fail... I suspect that replacing the unit is the only fix at this stage.

I'm not sure. Basically the reprogramming didn't work properly so now the car shows a red triangle for brakes. It basically has nothing other than unassisted manual brakes. No boost. No ABS. I'm not sure about B-pedal regen, but I'll guess that doesn't work either.

 

[DaveinOlyWA]

My guess is that something disrupted the flashing mid-progress and resulted in corrupted firmware. It could have been a power glitch, data glitch or something else. It is rare but not unheard of when updating firmware. Usually there is a graceful recover process built-in, but it can fail... I suspect that replacing the unit is the only fix at this stage.

I'm not sure. Basically the reprogramming didn't work properly so now the car shows a red triangle for brakes. It basically has nothing other than unassisted manual brakes. No boost. No ABS. I'm not sure about B-pedal regen, but I'll guess that doesn't work either.

Aaron also speculated the same thing

 

[DaveinOlyWA]

Update from Aaron;

I am here every saturday. That brake controller replacement is bogus. When you reprogram the controller it discharges the capacitor. If you dont follow Nissans directions for this reprogram and just use standard reprogram procedures for it you will end up with a capacitor that never recharges. My geuss is the tech will call nissan on monday and the car will be going monday afternoon.

 

[ztanos]

So the capacitor acts like a cache memory? I've never heard of capacitors doing this long term. Interesting.

 

[DaveinOlyWA]

So the capacitor acts like a cache memory? I've never heard of capacitors doing this long term. Interesting.

i dont think that is what he means. the capacitor is required to smooth out the regen and if it does not recharge properly it is probably throwing all kinds of errors to the brake controller

 

[TEG]

Capacitors don't store charge indefinitely. So it would "self drain" even if the car was left parked for a while. It probably doesn't store very much power so could get recharged quickly.
Even if they "emptied" it during the procedure, I would be fairly certain that it normally has a way to recharge itself from the main Li-Ion traction pack.
It would make no sense for the discharged capacitor to stay non-working unless something else was wrong too.

 

[DaveinOlyWA]

Capacitors don't store charge indefinitely. So it would "self drain" even if the car was left parked for a while. It probably doesn't store very much power so could get recharged quickly.
Even if they "emptied" it during the procedure, I would be fairly certain that it normally has a way to recharge itself from the main Li-Ion traction pack.
It would make no sense for the discharged capacitor to stay non-working unless something else was wrong too.
I would think corrupted firmware is a far more likely explanation, and the capacitor story is BS from someone who doesn't really understand the system.

guess we will find out soon enough but correct me if i am wrong but the capacitor should be running in a normally charged state and used for extreme power demands in emergency braking situations right?

 

[Stroked02F350]

Capacitors don't store charge indefinitely. So it would "self drain" even if the car was left parked for a while. It probably doesn't store very much power so could get recharged quickly.
Even if they "emptied" it during the procedure, I would be fairly certain that it normally has a way to recharge itself from the main Li-Ion traction pack.
It would make no sense for the discharged capacitor to stay non-working unless something else was wrong too.
I would think corrupted firmware is a far more likely explanation, and the capacitor story is BS from someone who doesn't really understand the system.

The capacitor is drained while the reprogram is done. Since the brake controller is offline while the capacitor is drained when it comes back it expects to see the
capacitor at full power. Since it is not there are several failure codes that shut the brake controller down and revert the car to a non-assist hydraulic brake system. The TSB lists a procedure to force the capacitor to re-energize itself. After that occurs the you can reset all the past system failures and the car is returned to normal function.

 

[DaveinOlyWA]

i offer the information as it comes to me. TEG; what is your qualifications for this subject? Aaron on the other hand is just some hack with a Master LEAF cerification

 

[RegGuheert]

Update from Aaron;

I am here every saturday. That brake controller replacement is bogus. When you reprogram the controller it discharges the capacitor. If you dont follow Nissans directions for this reprogram and just use standard reprogram procedures for it you will end up with a capacitor that never recharges. My geuss is the tech will call nissan on monday and the car will be going monday afternoon.

Perhaps he is talking about the ultracapacitor under the hump in the back? If so, that would take a while to discharge and to reenergize. Does anyone know the value of that capacitor? I'm going to guess about 300 Farads based on the size.

Thanks for the info! I may give them a call with this information on Monday.

 

[TEG]

The capacitor is drained while the reprogram is done. Since the brake controller is offline while the capacitor is drained when it comes back it expects to see the
capacitor at full power. Since it is not there are several failure codes that shut the brake controller down and revert the car to a non-assist hydraulic brake system. The TSB lists a procedure to force the capacitor to re-energize itself. After that occurs the you can reset all the past system failures and the car is returned to normal function.

Thanks - that seems like a plausible explanation. It sees an unexpected energy loss and triggers error codes requiring a reset before it will recharge the capacitor back up again.

The original description made it sound like the capacitor must always have a charge or else the whole system is ruined.

I guess the guys doing the reprogram procedure need to make sure to finish the whole procedure to reset the capacitor charging too.

 

[TEG]

That brake controller replacement is bogus. When you reprogram the controller it discharges the capacitor. If you dont follow Nissans directions for this reprogram and just use standard reprogram procedures for it you will end up with a capacitor that never recharges. My geuss is the tech will call nissan on monday and the car will be going monday afternoon.

With more context from Stroked02F350 now, I can re-read that in a different way from my first read through.

First time I read it, I thought:
"That brake controller replacement is bogus" = "the whole TSB doesn't work at all, don't do it at all."
Now with more context:
"That brake controller replacement is bogus" = "they botched a specific upgrade attempt by not finishing the full procedure."

First time I read it, I thought:
"you will end up with a capacitor that never recharges." = "by draining the capacitor it was ruined and will never recharge"
Now with more context:
"you will end up with a capacitor that never recharges." = "after doing the firmware update the tech also needs to reset the capacitor charge monitor or else it won't try to recharge it again."

 

[DaveinOlyWA]

ah, the joys of online interactions!

 

[GeekEV]

Sorry for the delayed response, folks - got sick. Anyway, yes I agree with what others have posted. The issue definitely seems to be fixed! Hooray!

Though the brakes still feel a *little* touchy at extremely low creep speeds...

 

[Nubo]

Is there a way to view this TSB without being assimilated by FaceBook? :roll:

 

[QueenBee]

Is there a way to view this TSB without being assimilated by FaceBook? :roll:

FaceBook doesn't have the TSB. I suspect you have to pay for the Nissan service manual subscription thing to be able to see it, unless your dealer shares it with you or someone posts it online.

 

[RegGuheert]

Good news! Nissan called and said the update is now complete! They let our LEAF sit over the weekend and the mechanic was able to complete the process this morning.

I had called first thing to let them know what had been said in this thread about reenrgizing the ultracapacitor, but it is not clear if that was the issue or not. I will post back if I learn anything more when I pick the car up in the morning.

I'm glad to be getting the car back without a major amount of work and with the improved braking software!