A Pentium B70 2.3L car with a mileage of about 68 thousand km and a B type engine that matches the FS5 A-EL automatic transmission system in 2008. User response: after the ignition switch is switched on, the dashboard does not show anything, and the reverse impact is serious. Fault diagnosis: first check the fuse of the instrument cluster and find that the 15A fuse of the instrument has been blown. Referring to the circuit diagram, it is known that the fuse is supplied by the ignition switch, the current enters the instrument panel, and the TNS relay and the instrument warning lights are supplied inside the meter respectively. I suspect that the instrument internal short fuse fuse, so decided to replace the fuse test. As a result, the fuse did not fuse after engine start, and the instrument showed normal. However, considering the fuse fusing indicates that there must be a short circuit in the circuit, we must find the fault point. Just when the road test was put into reverse gear, the meter did not show immediately, and the reverse impact occurred, indicating that the power supply circuit of the instrument was broken again. Checking instrument fuse found that the fuse fuses again. According to the circuit diagram, the reversing lamp is powered by instrument 15A fuse. So we check the reversing lamp circuit and find that there are obvious punctured marks on the left side reversing lamp wiring harness. When using the hand to touch the side of the negative line, it is found that a very small wire pierced the wire harness, resulting in a short circuit of the reversing lamp circuit, so that the transmission of the transmission will fuse, the power supply of the instrument is interrupted, and the display is completely absent. Troubleshooting: after repair of damaged circuit, trial run, troubleshooting.