Brakes locking up on 2019 Ultra

[Hossamania]

A friend has a 2019 FLHTK Ultra Limited, the rear brake occasionally locks up under braking rather than abs activating. This happened a few times yesterday, one time going downhill into a curve, tire locked, sent him on a slow lowside, luckily no injury or real damage, but of course shook him.
This has happened before, took it in and of course no codes found so nothing HD could do.
It seems to happen more frequently after he does a burnout or two, maybe messing with the system.
He's going to take it in again, get a full brake fluid flush and inspection.
He had a Harley cam and tune put in when new, and recently changed to aftermarket cam and tune, so drivetrain warranty (7 year extension) is void, but could HD claim the tune voids abs warranty too? The problem did arise early on after purchase in '19.
He says the brake will release when he releases the pedal, but will immediately lock up again even with light pressure, no way to modulate or threshold brake. Even after shutting the bike down, allowing a system reset per se, it will lock up again when riding, then the system may work properly. It is frustrating trying to anticipate the next braking action.
Any ideas appreciated.

[kd]

To me, it sounds like the issue is in the rear caliper, wheel bearings and / or ABS module.  It's either not kicking back the pads and releasing, boiling the fluid or there is air in it which will expand. Releasing the pedal should release the brake when the ABS senses the difference between the two wheel speeds but the fact it doesn't points to possible wheel bearings too.  Wheel bearings could also cause the dragging brake and heat.  There were instances discussed here of clogged / seized ABS modules doing this too.  Proper bleeding services may not have been completed  correctly and contributing to the failure of the ABS to cycle the release function when it happens.

[Coyote]

Does the lock up release when he releases the brake levers?

[kd]

Does the lock up release when he releases the brake levers?

   I failed to notice Hoss said it does release. That complicates the ABS module diagnosis a bit and brings in failing wheel bearings a bit stronger.  A cocked wheel upon application could possibly cause the pads to mechanically bind, lock up, and it would not be able to threshold brake the bike.  It's the kind of thing that could reoccur on subsequent applications too.   It also should be an easy thing to check off the list by jacking the rear of the bike up.

[Hossamania]

Thanks, now at least he's got a few things to look at.

[xlfan]

Is it possible that exposure to DOT 5 fluid could cause a behavior like this to the ABS module?

[Hossamania]

Factory serviced, no fluid change yet as far as I know, but it is definitely due. This has been going on for at least two years.

[rigidthumper]

Makes me wonder if doing the burnout sets an internal code, and temporarily deactivates the ABS? This is possible, due to the front wheel @ 0 MPH & brake system activated, while the back wheel is at 50 MPH. System thinks there's an ABS failure, so temporarily disables it.  Key off/engine off for 10 seconds after the burnout would reset the system, and should restore usual ABS function.

[Hossamania]

That's what we were thinking as well. He did shut it down at one point, but it didn't seem to reset, though it may not have been the full 10 seconds.
He did lay down one serious burnout leaving main street in town on a run Saturday, damn impressive. He seems determined to break this bike at every chance he gets, yet he wants it to be reliable to use it to go on long trips with the wife.
But I digress.

[cheech]

Makes me wonder if doing the burnout sets an internal code, and temporarily deactivates the ABS? This is possible, due to the front wheel @ 0 MPH & brake system activated, while the back wheel is at 50 MPH. System thinks there's an ABS failure, so temporarily disables it.  Key off/engine off for 10 seconds after the burnout would reset the system, and should restore usual ABS function.

The one time I did a burnout on my 2015 FLHTK. Front wheel locked, it set the ABS light.
Never tried to see if the ABS was deactivated.

[kd]

That's what we were thinking as well. He did shut it down at one point, but it didn't seem to reset, though it may not have been the full 10 seconds.
He did lay down one serious burnout leaving main street in town on a run Saturday, damn impressive. He seems determined to break this bike at every chance he gets, yet he wants it to be reliable to use it to go on long trips with the wife.
But I digress.

Sounds like a reasonable expectation. 

For the rear wheel (or either wheel) to lock up when performing a somewhat threshold braking application, the pads have to be engaging hard.  I do plenty of horrendous multi-gear burnouts (daily) without ABS incident.  Well OK, sheared the teeth off of 3rd gear a few times until I got a GrudgeBox. This sounds more like a mechanical failure of sorts.  The owner may however be applying more brake that he realizes or admits to due to his excitement. The ABS is failing to moderates the locked wheel at that point.  If he isn't over applying the brake it's mechanical.  It's also possible the ABS sensor wire at the wheel is failing but in that case the ABS light should indicate a problem.  Ask him if the light comes on after a fresh start-up and stays on until he starts to get rolling.

[Hossamania]

Will do.

[fbn ent]

kd.........."Ask him if the light comes on after a fresh start-up and stays on until he starts to get rolling."
That is supposed to happen ... correct? I always assumed it was a system check.

[Hossamania]

kd.........."Ask him if the light comes on after a fresh start-up and stays on until he starts to get rolling."
That is supposed to happen correct? I always assumed it was a system check.

Correct, it is a systems check.

[hrdtail78]

Does this bike have interlocking brake feature and hill hold?  Anything lighting up on the dash, such as an H?

[Hossamania]

He doesn't believe the brakes are interlocking, no Hill hold, no H on the dash.