Failure phenomenon: a 2008 models Beijing Hyundai Sonata 2.0 L sedan, equipped with HIVEC automatic transmission, mileage 40000 km. According to reflect the user, the vehicle traveling speed table pointer does not move, the transmission shock obvious sense, difficult to increase the speed of refueling.
check analysis: First, the failure phenomenon described in the user’s confirmation, there is a failure not only found the car user described, there are other problems. R vehicle rear engaged gear, reversing lamp is not lit, no self-test reversing radar alarm sound, there is no reverse image display screen on the DVD. Car reversing radar is the original configuration, but converted a DVD navigation, the installation of a reversing visual image.
of a transmission system using a fault diagnostic testing, fault code stored P0707, meaning transmission gear switch fails. After inspection of the relevant basic circuit, found position B, the engine compartment 20 of the fuse box / UP (10 A) on the blown fuse, the fuse box fuse only comments to this automatic transmission fuse, and I judgments based on experience, this feature does not fuse so simple. Thus the power distribution part of the original circuit diagram Now, parallel power supply found on this electrical fuse element comprises a transmission gear switch, a reversing aid system control unit, a vehicle speed sensor, the pulse generator A (input shaft speed sensor), a pulse generator B (output shaft speed sensor), and a backup light switch parking light switch, that is, if the elements described above, or any of a line short circuit, will result in the position 20 B / UP fuse blown. Binding fault code stored in the transmission gear switch, the maintenance personnel to replace the first fuse and switch gear, turn the ignition switch and clear fault code, loaded gear shift lever is pushed from the R range N, reversing lights and ready to check whether other systems back to normal, he heard ldquo; snapped rdquo; bang, No. 20 fuse has blown, it seems the problem is not switch gear.
FIG 1
disconnect switch gear harness connection terminal C09 (FIG. 1), measuring 7 feet (foot switch signal gear), find short to ground. Measuring the position of the fuse box 20 in the power output terminal of the fuse, is also short-circuited, the shift lever out of the R-range, short-circuit disappears immediately. Thus, the cause of the malfunction should be with other yuanPieces does not matter, it should be the reverse signal fault caused. As P0707 DTC storage, but also because the B / UP fuse is blown, inhibitor switch, a pulse generator and a pulse generator B A no signal output, and therefore only the transmission control unit stores the mistaken recording the fault code, the transmission control unit to give signal is less than the above several elements, will enter the safe mode, in the third speed forward gear lock, so there will be significant impact transmission, the vehicle speed can not reach maximum speed. No indication speedometer, but also due to the speedometer sensor and the pulse generator B did not cause a corresponding working power. After the fuse 20 is blown, the reverse signal is not transmitted to the various elements of the rear portion of the vehicle, the parking sensor system, the reverse image could not work and the backup lamp.
FIG. 2
Figure 3
Through the above analysis, I believe that the key to short circuit point to find parking lines in what position. Check according to conventional short circuit elimination, with reference to a circuit diagram of the various electrical components of the reverse signal according to a check. Open the deck lid, unplug the rear parking system associated with the vehicle taillight harness connection terminal, reversing harness connection terminal radar system, the installation of the detachable cable reversing video system, and then measuring the position of the fuse box 20, the fuse power output end, still short circuit with the body. It is line backup system exists for a short to do? That check up more trouble. But intuition possibility is not great, because the car is a 2008 model, the mileage is not much, except for when buying a new car to install a reverse image and change the DVD navigation, the other systems remain the original vehicle configuration, use More than a year are relatively normal, until a few days ago the problem suddenly appear. And then there are the line arrangement of Sonata cars are very standard, unless the human factor, otherwise the probability of short-circuit line is very low, so I think the final point of failure or in the luggage compartment. Then check the connections of several electrical terminal element luggage compartment, the luggage compartment there is then found on the left side a wiring harness connector plug RR11 (FIG. 2) is connected via a harness to go above the luggage compartment, the luggage compartment observed after two there are two side combination lamp, when sudden reaction I, above the luggage compartment combination lamp is down lights, pulled only a small lamp and turn signal harness connecting plug before mounting tail lampAt the rear, reversing lights and rear fog above the luggage compartment cover (FIG. 3). Then unplug harness connection connector RR11, the measurement position 20 the power output terminal of the fuse again, conduction phenomenon between the body and which disappear immediately. Further examination found that the right side of reversing lamp filament has been blown, blown filament and just ride between the two poles inside the bulb (4), is it a short-circuit filament cause it? It might not make sense! So why are disconnected from the reverse lamp harness connector, short-circuit between the power output of the engine compartment fuse box is in the No. 20 fuse with the body and disappear it? Replaced with a puzzled right reversing lamp, the mounting terminals and the line disassembly, replacement of the fuse again, turn the ignition switch, shift lever 20 is moved to the R range fuse numbers and blown. Sure enough, the problem is not so simple, in theory does not make sense, question how easily solve it?
Figure 4
Thus overhaul seems to have reached an impasse. After review of the repair process, maintenance personnel discovered a problem with the idea in front of the overhaul. Between a power output terminal and the relay box in the engine compartment of the vehicle body in position 20, if using a multimeter measurement, the conduction base is normal, and the right reversing lamp filament burnout cause an internal short circuit does not matter. Because reversing lights on the left side is normal, the power supply 20, the position of the fuse box in the engine compartment originally by reversing both sides of the filament lamp is then ground down lights, reversing lights on both sides are connected in parallel, filament resistance value of about 1 ~ 2 Omega ;, if only an ordinary multimeter to measure conduction condition, 1 ~ 2 Omega; resistance is almost negligible, is basically the direct conduction, so that the front of the inspection into the misunderstanding, but one thing is clear, short circuit lines do exist, otherwise the fuse will not blow into the R block immediately.
In order to more directly reflect the problem, we decided to change the method for detecting using inspection light again. One end of the test lamp is connected to the positive electrode of the battery, the other end position of the fuse 20 in the fuse box engine compartment power supply output terminal, when the pilot light is lit. Some electrical components individually and then disconnect the rear, when the two imaging systems backsliding broken line, the brightness of the lamp test undergone great changes. The battery voltage is constant, if a large impedance changes of the current will certainly change the brightness of the lamp will again AriakeThe significant changes. This reverse video cable 2 is a signal line to DVD trigger line, the other is a reversing camera operating potential supply line. Multimeter were measured and then a short circuit to ground line 2, and found to DVD trigger signal line is shorted to ground. Check the trend line down, the result of the rear seat in the car on the right side below the gum found in skin damage Ground signal line, bringing the real point of failure was only found.
Troubleshooting: fixed wrap broken signal line, the recovery line and removed before the fuse is mounted. Turn the ignition switch, a fuse 20 engaged again after the R range is not blown, the associated reversing system normal configuration, the impact of the road test transmission phenomenon disappears, smooth speed can reach 120 km / h or more, to this troubleshooting.
reviewed: the whole idea of the car troubleshooting is not wrong, but the early diagnosis of maintenance errors, when the reverse gear signal detection and body ground misunderstands the circuit works, on this separate For the line, ignoring the resistance of the filament is small almost even direct conduction, and service diagnostics Shique in it spent a lot of time. First short-circuit measuring line is disconnected in the above member, because many electrical itself is grounded through the interior of the vehicle body. For circuit diagrams, maintenance personnel often confined to visually see whether a few feet or a few turns on the terminal, whether short or open, in fact, there are many principle circuit diagram of knowledge, this is relatively easy for the professional automotive electrician who understanding, but for mechanical and electrical integration of contemporary maintenance workers, the need to strengthen the study and use in order to truly understand the circuit diagram schematics, circuit can quickly resolve the problem.
(Zhougui Ming)