Paragraph 1: The fault code is applicable to BMW, and P 1009 indicates the variable valve timing (VVT) control circuit-pilot sensor reset error (second row). In the power system, the electronic camshaft control valve (or oil control valve, OCV) adjusts the angle of the camshaft by changing the oil pressure of the camshaft adjuster (mechanical) according to the instruction of the engine control module (ECM), so as to ensure that the valve opens and closes at the best time and optimize the efficiency and power of the engine. Paragraph 2: The fault code is applicable to Audi. The common fault code is P 1009, which means MAF sensor 1/2- incredible load detection signal in Chinese. The mass air flow sensor 1/2 converts the air flow into an electrical signal and sends it to the electronic control unit (ECU) for fuel injection. Paragraph 3: Fault codes are applicable to Honda and Acura, and P 1009 indicates camshaft position sensor (intake/left/front)-circuit fault/front timing/system performance (line 1). The detailed meaning is that the camshaft position (relative position of the valve) is transmitted to the electronic control unit in the form of voltage signal by the camshaft position (CMP) sensor.