Shanghai Volkswagen Lavida car meter backlight why not go out

a 2009 annual Shanghai Volkswagen Lavida 1.6 L sedan, equipped with 09G type automatic transmission, there will be a background instrument lights lit phenomenon after users complained that the car sometimes lock your car.


After receiving the car, the test, as spoken by the user to the faults, the lock car dashboard lights lit background immortal (figure 1). Because not able to determine where is the problem, then the vehicle entered the workshop for further examination. But then repair more vehicles, so the car is placed about half an hour in the workshop. When I prepare for the car to be repaired, test found fault disappeared. It is connected to the vehicle fault diagnostic apparatus VAS5051B detects no fault of each unit of the vehicle control code storage. Then I looked Service Manual, careful observation instrument connector each terminal arrangement (FIG. 2), the Sunny car instrument no special control instrument background lights wires, a transmission signal is obtained by the CAN bus implemented by the vehicle unit BCM control activation.

FIG. 2

To facilitate troubleshooting, I decided to use a normal got the same vehicle were compared. I mainly wanted to see a black screen in the instrument, the instrument which case the user will be reflected under what conditions. After repeated operation, we found dashboard lights while the following cases: to open the door, open light switch, ignition key is removed, pressing the hazard warning lights and switches use the remote control unlocking. The author then these kinds of situations are analyzed.

(1) to open the door

Since the user of the indoor dome light switch is set to stop the door, if the door contact switch problem, in addition to the light turns the instrument, chamber dome light will illuminate.

(2) Open the light switch

If the light switch is a problem, then the open light switch, in addition to lights lit background instrument, also vehicle width lamp It will light up.

(3) remove the key

When the vehicle key is removed, the S terminal is disconnected, the instrument will stop the backlight is lit for a few seconds. If thisAspects of a problem, the situation will be accompanied by other electrical appliances can not be cut.

(4) pressing the hazard lamp switch

Now correlation circuit diagram (FIG. 2), the hazard warning lights when the switch is pressed, the BCM receives E3 the ground signal, thus controlling the turn signal lights, turning through the CAN bus and activate the indicator instrument and time / mileage lamp. When the switch is pressed again, E3 to ground, then the hazard warning lights canceled. Here we must note that the only E3 opened again, time dashboard / mileage lights will go out.

(5) remote unlock

When using the remote control unlocking, if problems arise, the lighting only a few seconds, not steady.

Figure 3

First, the author assumed that good CAN bus data line, whether the problem sequentially according to the above aspect of the summed inspection vehicle 5 . When checking the hazard lamp switch, we found hazard lamp switch (FIG. 3) is not very good return, causing the switch contact is not turned off, resulting in steady background light meter. After a slight grinding with sandpaper hazard lamp switch, does not interfere with the instrument panel when it is pressed, troubleshooting.

Summary: For the negative fault car, it is possible to check the hazard lamp switch in question, some luck. However, some failures sometimes encountered, especially when the non-sporadic fault sometimes difficult to inspect in a logical order. In addition to waiting for a failure phenomenon occurs again, there is a way few would think of as many possible failure, one by one investigation, doing so sometimes there will be surprises.

(Xuan Yi Wang)

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