Symptom: a 2004 Honda Accord 2.4 sedan, the owner reflects the car to open the door, the self-luminous instrument black screen. After the vehicle starts, the instrument still has no background light and any indication, and the shift lever can only be in the P position, can not change to other gears.
    Check the analysis: According to the user's description, this is the first time the instrument black screen failure. Maintenance personnel first search instrument fuse, found in the driver side of the multi-channel control box No. 21 meter 7.5A fuse blown, replace it, the instrument instructions return to normal, shift lever can also be linked to the corresponding gear. However, maintenance personnel know that the normal case of the fuse is not easily burned, only the instrument-related circuits in the presence of short circuit or electrical equipment current is too large, will fuse failure. So the maintenance personnel to check and instrument related to all the electrical equipment, and Honda fault detector HDS check instrument control unit, all normal, that this is an occasional fault, and the owner of an emergency car, this delivery.
    3 months later, the car again came to the store to repair the fault. Owners said that a month ago and two days ago, 21 fuse and burned 2 times, as with the first case, the owner on their own to find a repair shop to burn the fuse replaced, the solution of the urgent needs The But the same failure occurred three times, the owner determined to completely solve the problem. Maintenance personnel once again asked the situation when the failure occurred, the owner recalled an important detail, that is, when the failure occurred in the block. According to this clue, maintenance personnel to analyze the hanging D block to go through the R block and N gear, will not be the gear switch problem? Try to replace the gear switch, and then try to take the bumpy road and back and forth shift lever ,everything is normal.
    The next day and then test, hanging D block only heard "pop" sound, fault to reproduce. Because the shift lever when the shift is slow, obviously feel the fault is in the R gear when the occurrence occurs. Do not move the vehicle, and then put on a good fuse, the vehicle and all normal, it seems that the problem lies in the R-related lines and components. Maintenance staff was about to check the R-related lines and components, a colleague said, "is not a reversing radar is broken," the words awakened. Which the original models and no reversing radar, and this car is now the reversing radar is the owner of the installation. Because the installation of the parking sensor is a set of independent systems, and the line is not complicated, in the principle of simplicity, first check its line, and sure enough to find the problem.
    The original installation of the reversing radar power supply line is connected from the reversing lamp power supply line (the installation of reversing radar are generally from the power), but because the connection of the wire is too long, part of the line wrapped around the luggage compartment cover and Support institutions. With the luggage compartment cover often ups and downs, some parts of the connection line has been crowded thread, resulting in vehicle reversing lights between the line and the body short circuit. The transfer process, the shift lever through the R block, reversing lamp circuit power supply, due to short circuit, making the instrument line associated with the No. 21 instrument fuse blown. However, because the reversing radar to take the electrical line wear is not serious, so the short circuit here will happen occasionally, which also to the maintenance work has brought great difficulties.
    Troubleshooting: the reversing radar to take the wire will not be affected by the ups and downs of the baggage cover under the premise of the cut off for a period of time to restore the connection, and the wear and tear at the package, and the proper handling of the line to determine will no longer be luggage compartment Cover the bounce and support the mechanism after the extrusion, troubleshooting. After returning to the owner, the failure did not appear too.
    Review Summary: The root cause of this failure is the owner of the installation of parking radar, when the maintenance staff installed, the line processing more casual, resulting in the occurrence of this failure. Because the fault is incidental, the exclusion process if not in the test happened to happen, and maintenance without the accident that reminder, although the final can find the point of failure, but will undoubtedly spend a lot of energy. So, and then encounter a similar difficult or unusual line failure, we must first consider whether the car is not attached to the electrical (especially the new car), such as vehicle installation alarm, anti-theft and reversing radar, or modified audio System and so on. Because some of the irregular installation operations, maintenance process, will cause unimaginable failure phenomenon. In this also warn those relatively careless maintenance personnel, vehicle maintenance must be based on regular maintenance methods, especially in the installation of some electrical equipment, we must understand the principle, and then install, after installation to clarify the body line The Do not blindly work according to personal experience, so as not to cause unnecessary trouble.