a 2000 annual Shanghai Volkswagen Passat B5 1.8 L sedan, equipped with 01N-type 4-speed automatic transmission, the user initially not hot heater repair, reversing light bulb does not light failure. After the above-mentioned maintenance work is completed, there was a phenomenon of the engine can not be started.
take the car, I first ask the maintenance staff which work is done, the maintenance staff said the only user maintenance of the car repair faults. In the understanding of the relevant circumstances, I decided on the car is detected by the scan tool. Detecting the vehicle found not stored in the engine control unit fault code, the automatic transmission control unit stores the failure via ldquo meaning connection failure diagnostic apparatus; inhibitor switch does not define rdquo; DTC. I tried to clear the fault code, but can not be removed, you can determine the fault code is permanent fault.
FIG 1
FIG. 2
Based on past experience in the maintenance, when the vehicle appears vain vehicle, the starter does not work and there is a case where the vehicle fault codes occurs, generally for the inhibitor switch (FIG. 1) is damaged. Given the user to take the car in a hurry, it was decided to replace the switch gear. But the unexpected is, the replacement of the switch gear test failure remains. It then decided to switch the shift line inspection. According to the circuit diagram (FIG. 2) There are six car inhibitor switch line, measuring T7 / 3 Ground terminal pin as a switch, work; T7 / 1, T7 / 2, T7 / 6 and T7 / 5 feet switching output gear signal lines, through the normal fault diagnostic detection; T7 / 7 pin terminal of the switching power supply, the actual measurement voltage 0 V, the problems do here? The power supply lines can be seen, the switching gear 15 from the supply line to the fuse S231 (FIG. 3) for this line protection fuses. The inspection of the fuse, the fuse was found damaged. After replacing the fuse, test the fault persists.
Figure 3
At this time I feel somewhat confused, the normal line, the new gear switch, fuse replacement is also why the engine can not start it ? Is it a problem with the gear switch? So I try to go back to the old switch mounting gear. At this time, fault diagnostic reuse clear the fault codes, it isFault codes can actually be cleared, the starter test is working properly, the engine may be started normally. Later, new accessories, it was discovered a new switch gear itself is indeed a problem.
vehicle can be determined before the service is normal, then the fuse why would it be damaged? By a circuit diagram analysis, the author found that the reversing light and the transmission line circuit combined. Generally, for a car equipped with automatic transmission models 01N, the reversing light is lit is: R gear shift lever is engaged, the reverse gear position recognition switch, the reverse control signal is transmitted to the transmission units, the transmission control unit outputs a reverse signal to the relay, thereby reversing lamp lighting. And this is precisely the fault of the car in reverse lamp maintenance man finished after replacing the light bulb appears, fuse It seems repairman damage when replacing the lamp. Can be inferred, maintenance personnel in reversing lamp line is replaced when the reversing light lamp ON state, so that the relevant short circuit occurs, thereby damaging the fuse. When the fuse is damaged, not the power switch gear, such that the inhibitor switch is not working properly, the transmission signal is transmitted to the error (D range), resulting in the automatic transmission control unit controls the starter relay to terminate the starter working limits.
Finally, after the replacement of the fuse, and the replacement gear switch back to the original vehicle, test troubleshooting.
Summary: With the increase in modern automotive electrical equipment, circuit complexity increases. For vehicle maintenance personnel, the difficulty to determine the fault increases. So for modern vehicles, each with between appliances are linked, one bad it may cause more serious consequences. Therefore, maintenance personnel in the maintenance or replacement of vehicle electrical appliances, must pay attention to disconnect disassembly and maintenance work related with the electrical power supply and then to ensure that the vehicle will not be unnecessarily damaged. On the other hand, we must remind the maintenance staff, do not be too fault diagnosis on a single train of thought, we must continue to seek rapid and easy troubleshooting methods to improve efficiency and ensure quality of maintenance.
(Liangyue)