@Danal The code did the trick. Homing Z works like a breeze. Thanks.

@phaedrux I think the issue is the board is treating the bed heater like a nozzle heater. It is running tests with the fan on and fan off.

These codes:
M308 S0 P"temp1" Y"thermistor" T100000 B4138
M308 S0 P"temp0" Y"thermistor" T100000 B4138

They look identical. Perhaps there is a code for bed heaters.

@phaedrux Okay, I got things straightened out.

1. That loud tone was coming from my APC battery backup. The printer is now plugged into a surge protector.
2. Bed Heater is now connected to OUT 0.
3. Confirmed bed heater calibration still works.

Thank you very much for the guidance.

@phaedrux Okay, I got things straightened out.

1. That loud tone was coming from my APC battery backup. The printer is now plugged into a surge protector.
2. Bed Heater is now connected to OUT 0.
3. Confirmed bed heater calibration still works.

Thank you very much for the guidance.

@phaedrux I am worried I got it all wrong. I have my heater connected here:

@phaedrux So, based on your comment, I do not need the power supply feeding Out 2 (middle connector block), just the left (Out 1/Power In)

@phaedrux I will check when I get home.

@phaedrux I have my power supply feeding these leads:

@phaedrux When the heater is first warming up from room temperature, there is a loud, continuous tone coming from the board. After it reaches the target temperature, the tone stops. Even when the temperature drops, the tone does not return when the board engages the heater to warm up again.
I am not sure if this helps but I have both outputs from my power supply feeding the 2 inputs to the board. When I first got the board, a Facebook group advised me to set it up that way.

@dc42
Out of an act of desperation, I ran the calibration again.

M307 H0 returns this:
Heater 0 model: heating rate 0.377, cooling time constant 62.4, dead time 1.54, max PWM 1.00, calibration voltage 22.7, mode PID
Computed PID parameters: setpoint change: P307.5, I31.363, D331.4, load change: P307.5, I69.412, D331.4

I must be crazy. This is the 5th time I ran M303 H0. This time, it worked. I just wish I could silence the long beep or at least lower the volume during the initial warm-up. It's probably a necessary safety feature.

Should I be concerned with the warning: Warning: M307: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 209C?

@phaedrux Calibration finished with the same error code:

Warning: heater behaviour was not consistent during tuning
Auto tuning heater 0 completed after 3 idle and 25 tuning cycles in 3658 seconds. This heater needs the following M307 command:
M307 H0 B0 R0.377 C62.4 D1.54 S1.00 V22.7
Send M500 to save this command in config-override.g

It still errors out about the heater taking too long.

@phaedrux Yeah, it's still running tests with the fan. I'll see if the error goes away after the test.

@theruttmeister My bad, for some reason I was thinking T as temp probe, not tool. Using the code M303 T0 S60 goes to the nozzle. I need this to test the bed heater. I'm not sure what code I am missing.