ignition is cutting off for a split second

Honda Civic 2002 1.7, when driving the car, it's seems like the car switches off for a split second and the engine management light shows for the split second. The rev counter drops. When cutting out sometimes the enigine management light stays on rev counter down, no power, and when for a split second cutting out again the car is okay.
When the car is placed on the diagnostic machine no faults recorded on the computer box
no codes