PREHEAT_CHECK

[gcode_macro PREHEAT_CHECK]
gcode:
    M117 PREHEAT CHECK
    G4 P18000
    {% if printer.heater_bed.temperature < 40 %}   #if heated bed is below 40 do the next thing
        M117 PREHEAT STARTED
        ABS_PREHEAT
    {% else %}
        M117 PREHEAT CHECK COMPLETE
    {% endif %}