A method is proposed for synchronizing a combustion engine in a hybrid vehicle provided with an electric motor, comprising the following steps: applying an initial rotation speed setpoint value to the electric motor (typically 2,500 revolutions per minute), then synchronizing the combustion engine on the basis of the rotation signals from the camshaft and the crankshaft. In the event of a camshaft signal failure, an initial combustion engine position assumption is selected from among a plurality of possible assumptions, and injection tests are performed by adjusting the rotation speed setpoints. Once the idle speed setpoint has been reached, the rotation speed setpoint value of the electric motor is reduced to a new value (typically 2,000 revolutions per minute). If the assumption is confirmed, the speed setpoint process is stopped; if not, another assumption is tested until confirmation occurs.