What does a service involve?
Check insulation on internal wiring.
Earth test throughout the cooker.
Test voltage, load and resistance.
Check operation of the elements.
Check operation of any vent fans.
Check operation of any PCB, including tests to see how the PCB responds.
Check any safety devices.
Clean any circulating fan present.
Check communication of any handset.
Check for general safe operation of the appliance.
Cosmetic checks ie. lid adjustments etc..