• Brew temperature
• Pump pressure
• Steam pressure/pressure stat function
• Coffee volume
• Water level probe clean and verify function
• Wear of grinder burrs (if applicable)
• Steam valve function and possible leaks
• Water condition
• Water filters and softeners (if applicable)
• Screen screws
• Function of button pads
• Brew valves checked for pressure release and leakage

Replace:

• Gaskets
• Screens
• Pump Capacitor (if needed, additional charge for part)