From my understanding my 2002 3rd Gen shares a similar ABS/Master Cylinder with your 4th Gens.

Symptoms: Prolonged motor cycling-whirring sound upon startup. Squishy brake pedal and rig lurches forward when almost at a stop, while making motor-whirring sounds.

Physically inspected all connection harnesses at the ABS unit as well as speed sensors at each wheel and they seem to be fine. No breaks etc.

Picked up a complete ABS/Master Cylinder unit from a local guy for $150 so I'm going to swap it out to see if it helps.

When I changed my brake fluid last year I just bled the system old school. I had no idea that I needed to trip the ABS actuators so it's probably why my brake pedal is still squishy.

Is there a less expensive option to trip that ABS actuator, to 100% bleed, other than purchasing a scanner with ABS auto-bleed option? (Which is like $200)

Also I read something about zero pint calibration and I'm wondering what that is and if I need to do it.

Any help appreciated

I have read that if you do several "panic" stops from fairly moderate speed that will trigger the ABS which will trigger the actuator to help get any air out of the ABS system/actuator, so I would do that a few times and then bleed the brakes normally, then rinse and repeat until it seems that you got all the air out/the pedal firms up.

Of course do the panic stops on a seldom used road where there's little to no traffic!!

It is my understanding that you would only need control of the solenoids if you replace the cylinder and don't bench bleed first prior to install. I bled my brakes a few months back the OG way, and I have had no issues. To me, it sounds like the seal on the piston in your master cylinder may be failing, and you're losing brake pressure as a result. Did you have the same symptoms prior to flushing?

As to your question on zero point calibration: unless you replace an electrical component of the ABS system (including the cylinder, I'm assuming) your ABS computer will see this and throw out a traction control light, which you would then need to calibrate to correct. Even when tripped, the brake system on 4th gens still works as normal minus ABS. So I don't really think this is your problem

Yeah, that's what I'm thinking. And yes, it's been doing this for a quite a while and even prior to my flushing and replacing the brake fluid.

I'll have to do some research on how to zero point reset an 02.