Fault Diagnosis Method Of CMP Sensor

Fault Diagnosis Method Of CMP Sensor

Date:Mar 15, 2021

The effect of CMP Sensor failure

The CMP sensor is installed at the position where the camshaft runs synchronously, and provides camshaft position information. The camshaft position sensor has a great influence on the emissions of the system. When the sensor has a problem, it is difficult to start the vehicle, and the acceleration will be obviously poor when starting.

The ECU judges the cylinders based on this signal and the G28 signal, so as to determine the first ignition when starting; to determine the ignition sequence, and it is also used for sub-cylinder knock control. If the sensor fails, the engine has no knock control function, and the ignition advance angle of each cylinder is delayed.

cmp sensor15278174338

Fault diagnosis of camshaft position sensor

When the actual camshaft position does not match the commanded position of the electronic control unit, it will cause the CMP sensor to malfunction. One is an electronic failure, and the other is a mechanical failure caused by the accumulation of foreign matter on the signal plate at the rear of the camshaft and the damage of the signal plate at the rear of the camshaft.

(1) The sensor and its circuit are faulty

When the command solenoid valve is de-energized, the engine control module detects that the intake camshaft position actuator solenoid valve and the exhaust camshaft position actuator solenoid valve continue to open for more than 1s or cumulatively up to 5s, and the camshaft position sensor malfunctions.

When the command solenoid valve is de-energized, the engine control module detects that the exhaust camshaft position actuator solenoid valve circuit continues to open for more than 1s or cumulatively reaches 5s, and the camshaft position sensor malfunctions.

(2) Sensor fault code information generated by a fault other than the sensor itself

For example, in an Audi Q5, due to the poor performance of the oil pressure regulating valve, the oil pressure cannot meet the requirements of the camshaft adjustment device, which affects the timing adjustment function, so fault code P0341 is generated. The fault code set by the engine control module may only be a superficial phenomenon caused by the fault point, and the real fault source does not lie in the sensor itself. Replace the oil pressure regulating valve, and the fault is completely eliminated.

CMP sensor detection and precautions

Turn off the ignition switch, disconnect the camshaft position sensor, turn on the ignition switch to the "ON" position, use a multimeter to check the voltage between the VC terminal and VV-, it should be 5V, if there is no 5V voltage, check the wiring with the ECU separately. If the connection is normal, it means that the engine ECU is faulty.

Previous: What Is The Function Of Cmp Sensor?

Next: When To Clean Car Fuel Injectors