A Honda km accord with a mileage of about 185 thousand km in 2006. The vehicle is new for the accident vehicle, but the meter is not changed. When the test is completed, it is found that all the instruments are normal. Only the oil meter pointer does not respond and is located at the lower limit. Troubleshooting: the meter is displayed as a simple part of the body electrical apparatus, and its structure and principle are very simple. When the fuel level changes, the oil float also changes up and down, which changes the resistance of the sliding resistance and changes the current of the coil, so that the magnetic field change pointer is deflected to the corresponding angle. After understanding the principle, it is decided to detect it from three aspects: meter, sensor and circuit. First, HDS is used to adjust the code without fault code. Then the instrument is tested, the signal line of the oil pump is found at the plug terminal of the instrument, and the signal end is directly tied, and the pointer is changed from small to large, indicating that there is no problem in the fuel indicator in the instrument. Then the sensor is detected, and the two ends of the meter are measured with the resistance meter of the multimeter, and the float is turned, and the resistance gradually changes. The sensor has no problem, is the problem out in the circuit? There is no short-circuit phenomenon in the circuit with Multimeter resistance files. The problem is strange. All parts of the system are normal and malfunctioning. Are they normal when they are linked together? Plug the plug, use a test lamp to test the oil pump signal end whether there is voltage, the light pen is very bright, the voltage from the instrument should have a part of pressure drop, the light should not be very bright, why is this? Simply connect the pen to the circuit, move the sensor, and the brightness of the lamp is constant. Remove the plug of the instrument, the result of the test lamp is still bright, the reason is that there are other power lines in series in the circuit, using a multimeter to measure the signal plug voltage of the oil pump is 12V, more illustrating the problem. After careful search, it is found that there is a softening of the wiring harness of the rear seat oil pump. Once the peel is opened, the insulation skin is broken, and the internal connection is broken. Maintenance summary: due to the connection of the power line and signal line, the voltage on both sides of the pointer coil is 12V, causing the pointer to remain unchanged. It is not easy to find fault points in the analysis of all parts involved in this fault, but the whole system becomes easy to solve. Therefore, the maintenance personnel should learn the way of thinking from zero to whole.