This bulletin applies to 2011 Honda Fit vehicles. If the customer complains about a loss of power, but the vehicle checks out OK and has no set DTCs, the issue might be the normal workings of the brake override system.
The system is designed to cut engine power it is senses that the accelerator pedal might be stuck (the pedal is open and the brake pedal is pushed). If your customer rests his left foot on the brake pedal while driving, the system will think he's trying to slow down and the vehicle will cut engine power.
Before troubleshooting, ask the customer about their driving habits. It might just be the nut behind the wheel.