Car mileage only 3000km, the engine model cars 4GB1.3C of JAC with Auto Diagnostic Tools Wyatt . Users report: car engine fault lights lit , difficulty in starting , when in motion normal acceleration, engine response is very slow, slam the accelerator pedal without the normal reaction of the 4 ~ 5s , 5s the normal speed.
After the pick-up : The detector diagnostics, fault code is P0340: VCP intake camshaft position sensor status diagnosis , start the engine after clearing the fault code , fault lights immediately. Analyze the reasons for failure are as follows : ① camshaft position sensor connector plug is not real ; ② camshaft position sensor reference voltage circuit is open ; ③ camshaft position sensor signal to open ; ④ camshaft position sensor signal line open ; ⑤ camshaft position sensor improper installation location or damage ; ⑥ ECM interface failure ; ⑦ valve timing wrong.
First, camshaft position sensor harness connection plug checks without exception ; using a multimeter to check the camshaft position sensor 5V reference voltage signal to 0V; conduction file directly with a multimeter to check the camshaft position sensor signal line to the ECM plug conducting the case to pieces 05 horn , normal ; then the ECM and ECM connector pins carefully examined , without exception . Camshaft position sensor , ECM, VVT control valve replacement parts experiments were carried out , the fault still shows these components properly. With a detector interface into the data stream , to view the actual position of the intake camshaft angle is zero , display data , mainly on the camshaft position sensor signal wheel and valve timing system prompts carefully check the fault code and data streams . Remove the valve cover , first check whether the camshaft position sensor signal wheel loosening or displacement sensor signal wheel assembly firmly , no shift phenomenon . Go on a cylinder of the engine stop position , the first stop on the alignment position of a cylinder crankshaft belt pulley , and then check the intake and exhaust camshaft position of a cylinder is normally only found that the intake and exhaust camshafts cams a tooth is wrong on one cylinder position to adjust after being cleared before ending with a detector fault codes , start the engine fault light goes out , then start smoothly, significantly shorter start-up time to begin the road test after assembly completed , road test result is normal , when the engine throttle speed significantly , thus troubleshooting.
Maintenance Summary : 4GB engine crankshaft sprocket interference fit assembly methods, engine timing mark is usually through the timing chain 3:00 mark to make autel maxidas ds708 judgments. Noted above case , if the crankshaft or camshaft sprocket sprocket limit is not reliable, then the process will be running the engine timing position swimming phenomenon resulting engine difficult to start or accelerate weakness and failure alarm lights and other phenomena . JAC 4GA engine crankshaft sprocket is fixed by the key groove of the shaft on the crankshaft , 4GA keyway if engine wear , engine timing deviation will occur , resulting in inability to accelerate the failure modes consistent with 4GB substantial cause engine failure .
Comments : This case is a typical hard fault fault : fault code is present and can not afford to clear the fault phenomenon always present. Because there is a clear failure boot information , so hard faults in the range of relatively infrequent failure to acknowledge the fault is much easier. Therefore , the authors carried out a detailed reason for failure analysis . But note that, in the analysis of the cause , we can learn from the practice of ” fault tree ” or ” fishbone diagram ” , and press the categories of failure analysis , and then as VAG TACHO USB the investigation progresses, then gradual thinning causes. The case of the analysis of the cause of the malfunction is no principle here , know if the fault re- complicated case, such as the analysis of the causes of the end , it will be a huge space, exactly where to start troubleshooting becomes very difficult. If the cause of the malfunction is divided into : camshaft position sensor circuit failure, component failure , the valve timing faults in three aspects , maintenance ideas will be much clearer. In addition , the authors if we can use dynamic data flow information , will be able to indirectly identify work status VVT system , provide an effective basis for the search point of failure. As a new car with less than 3000 km appeared timing gear case should not jump teeth it is , it seems, at the same time we support domestic products , domestic products more deserving self .