Ignition switch is turned on but do not start the engine, the control computer will begin to enter the initial state, and the entire control system for self-examination, the fault indicator is lit. If the fault indicator is not lit, it indicates a fault line fault indicator should be checked and repaired. Turn the ignition switch or a moment after the engine starts, if the fault indicator is off, the control computer does not detect electronic control system failure; immortal if the fault lamp is lit, it indicates that the computer control system is faulty, then the square can read fault codes.