The mileage is over 350 thousand km, with 2008 TOYOTA Camry cars equipped with 2.4L engine. Customer reflection: the vehicle idling jitter serious, at the beginning, technicians according to their own experience to repair the car, respectively, the following work for the vehicle: cleaning the throttle body, who wash oil fuel oil, replacement spark plug, cleaning jitter and so do not exclude the car failure, each time to A treatment once a fault will disappear for a period of time. But then it will happen again. Fault diagnosis: failure may be analyzed as follows: (1) excessive carbon accumulation in engine; second, misalignment; third, insufficient cylinder pressure; 4 ECM; 5. First, using the endoscope to check the carbon deposit in the engine cylinder, there is not much carbon deposition. The cylinder pressure is tested by cylinder pressure gauge. The car has the fault code of DTR. The fault code is P0352. According to the instructions of the DTR, it begins to measure the line of the ECM to the ignition coil, disconnects the C11 to C14 ignition coil connector, and disconnects the ECM connector side resistance of the C24: C11-2 to C24-81, C13-2 to C24-81, and the standard resistance is below 1 Omega, the first technology The resistance of the tester is less than 10 when measuring the connector, but when the technician again. When measuring the connector, the resistance is infinite. The technician thought that it was the problem of the multimeter, then a table was replaced, and again the measurement was infinity. At this time, the technician suspected that the C24 connector to C11, C12, C13, C14 connectors had a bad contact between the lines. Use the multimeter to measure the ends of the connector and sloshing the harness. When the technician swakes the harness near the camshaft position sensor of the valve chamber, the resistance changes on the multimeter. It is doubted that the wiring harness is in trouble, but the harness of the car is not damaged or repaired in appearance. After peeling, it is found that there are white hard objects like gypsum in the harness of the site and the wire harness here has been broken. The resistance numbers of the multimeter will change when the harness is gently sloshing, indicating that the fault point is here. All the wire harnesses were stripped and found that all the harnesses here have changed into white hard objects (as shown in Figure 1), and the white hard objects have been cleared away. The failure of the vehicle may be due to the long time that the vehicle is used and the harness has been carbonized in the high temperature bake line of the engine, which leads to the larger resistance and less current in the line, and the spark energy shortage caused by the spark plug ignition is caused by the engine idle jitter, and the final ECM checks out the DTR newspaper. There is a fire in the 2 cylinder. After repairing the harness, the car failed again.