Brakes Fail upon Powering On

[JHKenney]

I had this exact same phenomenon with a 2017 30 kWh Leaf, which was supposedly not part of the recall. It was towed to the dealer, which said the problem did not manifest the next morning. So perhaps it was the same issue, cold-related, though the temp was only about 45F.

[markrshort]

I have also had this exact issue on my 2016 Nissan Leaf 30kw tekna. The problem has almost caused three accidents now and each time I take it to the dealership I simply get 'we cant fix the car if we cant replicate the problem'. Nissan Customer services have been as equally useless and keep telling me the same thing.
After reading extensively on this forum I understand that a 12v in bad health can cause boot up issues . I saw more issues with my car during lockdown as I was just driving to the supermarket 10 mins away once or twice a week. Is it possible that the car did not have enough time to charge up the 12v again during those short journeys and the parasitic drain zapped the 12v while the car was stationary? Is it worthwhile just turning the car on for half an hour per day to charge the 12v via DC-DC convertor or better to remove the battery and charge it in my flat. (i dont have a garage to use a trickle charger). Is it also true that making sure the climate control is on during journeys will boost the voltage going through the 12v and therefore charge it?
I have taken the car to an independent specialist and he has also found no faults with the car but he is changing the brake fluid - i'm a bit sceptical about this but its worth a try.
Has anyone had the intelligent braking control unit replaced in order to fix this issue? Apparently a new one costs £3000 so I would be incredibly reluctant to do this if I can avoid the situation and just keep an eye on the 12v.
This issue is causing me a ton of stress as my partner is expecting a baby in October and i'll obviously need a car when the time comes.
At the moment, its looking like I will have to sell up for a huge loss to a brokerage who buys faulty vehicles.
Any help would be hugely appreciated.
Mark

[bobkart]

I had this happen today. Drove 10-15 minutes to a store, shopped for 10-15 minutes, then upon starting I had very little brakes. Pedal went nearly to the floor, and when the brakes did finally engage, it was abrupt and noisy (clicking/whirring/bumping sounds). Battery voltage seemed okay (12V-13V resting, 14V+ under charge). Plus I have a LiFePO4 battery, which is supposed to help with the Leaf 'undercharging' problem. It was somewhat cold: we had a bit of snow last night, and just before that a lot of rain, and on a short drive during heavy rain, I drove through some large puddles, creating lots of spray. I just mention that as something could have gotten wet? But then I would expect the failure to not wait until the next day.



I had the car towed to a nearby dealer. Having read this thread since then, I may have been able to get it home and try a few things. I suppose if the LiFePO4 battery is failing, that could explain it, but as mentioned, voltages look good (on a cigarette lighter voltmeter). I get that a 12V battery load test is more telling of battery failure, but I wasn't in a position to do that test. The dealer might do that; we'll see what they say tomorrow. I have been getting intermittent Air Bag dash icons and DTCs (B00A0 0008 AIR BAG is still showing above), and those have also been blamed on 12V battery problems, so maybe that's it. And that seemed to start a few weeks back when it was very cold for a couple of days (below freezing).

[LeftieBiker]

but as mentioned, voltages look good (on a cigarette lighter voltmeter)

The lighter socket is only hot when the car is on, so in Ready mode you'd get normal voltage because of the DC-DC converter. Try it in Accessory mode - briefly!

[bobkart]

but as mentioned, voltages look good (on a cigarette lighter voltmeter)

The lighter socket is only hot when the car is on, so in Ready mode you'd get normal voltage because of the DC-DC converter. Try it in Accessory mode - briefly!

Right . . . I did cycle through the modes at one point, and that's when I saw the lower voltages I mentioned (in the 12.x-volt range). Once in Ready Mode, I saw 14.x volts, which of course would mask any 12V battery problem.

I forgot to mention that I went under the hood, and saw a normal brake fluid level, and nothing obviously leaking/loose/broken/missing around either of the master cylinder or the ABS distribution block (on the passenger side of firewall, with the handful of hard brake lines connected to it).

EDIT: Also the ABS, brakes (?), and stability control icons on the dash were lit (yellow):

But not the Tire Pressure icon (and not my picture, just borrowed from one of the videos posted earlier in this thread).

[LeftieBiker]

IIRC, the issue is condensation in the brake booster freezing, and the fix (?) was to keep cycling the booster often, by means of a programming patch, in sub-freezing weather. Sounds like a pretty crappy fix to me, though...

[GerryAZ]

All of the CAN Bus communication errors shown in the Leaf Spy screenshot of DTC's along with the brake symptoms described are strongly indicative of a weak 12V battery during starting (boot up) of the car. Once the 12V battery issue is addressed and DTC's are cleared, the braking, stability control, and ABS should function normally. It may take several attempts to clear DTC's along with disconnecting/reconnecting 12V battery several times to clear all of the communication fault codes and restore normal operation.

[goldbrick]

Since the brakes are hydraulic isn't there some kind of fail safe mechanism in place so that even without the brake booster the brakes will still work, at least like non-power brakes?

[bobkart]

Thanks for everyone's help. I called the dealer and they're just finalizing the estimate (waiting on a price for part of it). Talk of Intelligent Braking Modules and wiring harnesses needing to be replaced, due to some 'mysterious miscommunication' on the CANBUS. I don't have the number yet, but I'm sensing over $1,000 in this estimate.

I'll be bringing my LeafSpy Pro and dongle, and (at least) a 10mm wrench (to allow battery disconnection). I'm thinking of adding a battery switch at some point, to remove the need for a wrench in the future. I'll be trying the DTC Reset process in combination with battery disconnection (repeatedly if necessary) to get this resolved. My understanding from the forgoing discussion is that if you can get past bootup with none of these problems, you're safe to drive (as in, the problem won't manifest in the middle of the drive).

[ydrape]

Thanks for everyone's help. I called the dealer and they're just finalizing the estimate (waiting on a price for part of it). Talk of Intelligent Braking Modules and wiring harnesses needing to be replaced, due to some 'mysterious miscommunication' on the CANBUS. I don't have the number yet, but I'm sensing over $1,000 in this estimate.

I'll be bringing my LeafSpy Pro and dongle, and (at least) a 10mm wrench (to allow battery disconnection). I'm thinking of adding a battery switch at some point, to remove the need for a wrench. I'll be trying the DTC Reset process in combination with battery disconnection (repeatedly if necessary) to get this resolved. My understanding from the forgoing discussion is that if you can get past bootup with none of these problems, you're safe to drive (as in, the problem won't manifest in the middle of the drive).

I had problem very similar to yours on a 2015 Leaf. See below the parts replaced and their cost I have found by part number on the web.
Hopfully, parts and labor passed on warranty in my case.

DTC U1000
DTC U110D
DTC P3195
DTC U1008

https://drive.google.com/file/d/1wsvIb2 ... sp=sharing

Good luck!