"Check Regenerative brakes" error after diy front brake job

I've had front brakes apart a couple of times [even written up by now] but never actually replaced
any pads/rotors. I did push the pistons back a little to make reassembly easier, but no
complaints from the car. I would give it a couple of drive cycles and make sure you bed those
new pads correctly anyway, by doing a few hard but smooth slowing events IN NEUTRAL to
make sure regen isn't helping, let the hydraulics adjust their null position and the car to
reboot a few times, and see if that shuts it up. Unless you omitted something critical,
I would expect this to be easily fixable.

Were your old pads in that bad shape? It took like 12 years for me to be even a little bit
concerned about the fronts in the Prius, and I had put those suckers through hell in
the mountain roadtrips.

_H*

 

Replacing the brake fluid is a job I need to tackle soon. The dealer has done a good job for minimal dosh in the past but I'm concerned now that they'll put an end to the lifetime record I'm trying to set with my OEM 12V battery.

With the car "off" the brake system appears to default to conventional legacy plumbing. At the conclusion of a simple flush, I'd expect that if the pedal height was re-established before the Kona was powered-up again, the system would pass the ABS self-check none-the-wiser.

 

Wait, based on the "Check regenerative brakes" error message I'm wondering if you messed with the hydraulic brakes or the regenerative brakes?

 

It's all connected since the foot pedal is one way of initiating and controlling regen in H/K EVs, during which time pedal resistance is simulated hydraulically by an electrically-driven cylinder.

Regen is always used when foot braking instead of the disks, except when driving at very low speeds, when in Neutral or if the traction battery is at 100% charge.

I know Tesla does not have this feature and if I'm not mistaken, nor does Mini.

 

I considered the word "regenerative" in the warning message to be misleading because the OP did nothing to disturb the regen part of the braking process. Can't the Kona differentiate between a problem with regen braking vs a problem with hydraulic braking rather than lumping both kinds of problems into a single, less-definitive warning message?

 

It’s not unusual in any car for one problem to cause error messages from dependent systems.

 

Here's my $0.02 worth.
There is a motor-driven hydraulic cylinder that provides a power assist function to the pedal under friction braking, but also provides pedal resistance under regen, aided by a mind-bending arrangement of solenoid and check valves,

I'm assuming you've powered-up the car with the caliper pistons retracted somewhat, placed out of their normal short reach to the pads and disks.

On power-up self-test, like other ABS systems the pump activates to contact the disks and establish or verify the working range. If the power cylinder reaches the end of its travel, or at least exceeds the travel it expects to use it could fail the test. A traditional ABS pump on an ICE car is a vane type that has no limit to the fluid volume it can move, but not in this case. I suspect (well, I'm certain) that a ball-screw driven cylinder pump is used because the relationship between motor torque and fluid displacement is linear and bidirectional, with low hysteresis.

Once the piston is sensed to move further than expected, ABS and all related brake functions are going to fail their initialisation tests and the system will default to what they call "backup operation", emulating a conventional non-boosted hydraulic brake system.

I haven't tried this yet but I would expect that after flushing the system or replacing/cleaning pads and disk, you should pump up the pedal slowly before power-on. Until I understood how it reacts, as a precaution I would probably disconnect the 12V battery while working on the brakes.