Abstract: A monitor system for indicating the existence of one or more undesirable operating conditions of an engine-powered vehicle, and including three separate indicator panels. The first panel is energized prior to starting the engine and indicates individual prestart-condition faults, the indicators being disabled after the engine is in operation. The second panel indicates individual operating-condition faults and gives warnings of a different magnitude depending on the criticality of the faults. The third panel is for sevice faults and latches service-fault indications for general presentation to the vehicle operator and individual presentation to service personnel after the vehicle has been shut down.