Abstract: Pre-trip operational methods and procedures for automatically checking predetermined functions and the operating performance of a transport refrigeration unit which includes a refrigerant compressor, and a prime mover for the refrigerant compressor which includes an internal combustion engine. The methods include the steps of measuring the current draw of predetermined electrical components with the prime mover stationary, starting the engine when the current draw is normal, determining if the speed of the engine is in an allowable range, commanding the unit to operate in a cooling mode, checking for adequate cooling capacity as a dynamic function of the temperatures of the return air, discharge air, and ambient air, commanding the unit to operate in a heating mode, determining if the unit is actually operating in the heating mode, and preparing an indication of a fault condition descriptive of any detected malfunction and/or marginal operating performance.