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what causes a speedometer to be inaccurate
What causes a speedometer to be inaccurate:
1. Generally, the engine speed is high and low, due to uneven air intake or oil supply, or carbon deposition, resulting in unstable performance;
2. If it is in winter, the weather is cold in winter, the oil is semi-solidified, and it is normal for the rotational speed to be unstable at the beginning;
3. It may be that the vacuum tube has fallen off or there is air leakage. It is recommended to go to the after-sales service for maintenance.
The speedometer of the car is inaccurate. If the error is large, it generally depends on whether the tire size of the car has changed. If the tire has not been changed, the slippage is likely to be caused by the fault of the odometer sensor. It may be that the idling speed of the engine is very high. You can check whether the basic water and oil levels are normal. If not, go to the repair shop for maintenance.
There are three reasons why speedometers are not allowed. The first is that the speedometer sensor is malfunctioning. Second, there is a problem with the wiring between the instrument and the sensor. The third is a problem with the instrument pointer. Generally speaking, the probability of the latter problem occurring is very small and can be basically ruled out. It is recommended that the car owner go to the maintenance department and have the maintenance personnel check the odometer sensor and replace it.
Determine whether the sensor or instrument is faulty:
Close the sensor connector, turn on the ignition switch, the No. 2 electrode in the connector connected with the red wire on the brown background, stick out with a self-made wire with a plug, make a virtual trip on the ground part of the body, and input a pulse signal wire to the meter superior. At this time, if the pointer of the speedometer rotates, the instrument is normal. The fault is on the sensor's reed switch tube or magnetic ring. At this time, if the pointer of the speedometer does not rotate, it means that the instrument or the connecting line is faulty.
Judging whether it is an instrument fault or a line fault:
Remove the instrument panel, without unplugging, and measure the three electrodes on the meter with a multimeter. Turn on the ignition switch, the power line from the No. 26 fuse to the speedometer should be 12V to ground; use a multimeter to cut off the measurement, the resistance of the same pulse signal line from the instrument to the sensor connector should be zero, and the resistance of the grounding electrode to the ground should be zero. If the actual measured value is inconsistent with the above three values, the open circuit fault in the line should be excluded. If there is no fault in the circuit under test, it means that the speedometer is faulty and should be repaired or replaced as appropriate.
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