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What’s wrong with the Buick GL8 gauge backlight not coming on?

Vehicle information: A new 2014 Buick Land Cruiser commercial vehicle with approximately 65,000km has a 2.4LLE5 engine and 6T45E automatic transmission.

Fault phenomenon: This vehicle was reported for a meter backlight that was not illuminated.

Fault analysis: After receiving the car first to confirm the fault phenomenon, open the parking light switch, the car outside the parking lights can be lit normally, the combination of instrumentation is indeed no backlight, but the combination of instrumentation on the needle of each meter can be normal red.

Also, the buttons on the radio and air conditioning panel will not light up. Suppose you turn on the parking light switch with the ignition. In that case, you will notice that the information display center screen on the combination instrument and the screen on the radio go from bright to dark, which indicates that the combination instrument and radio have been given the information that the parking lights are on.

Read the fault codes of the whole vehicle with a diagnostic instrument, and no fault code exists. By reading the input data stream of the body control module, it is found that when the parking lights are turned on, the status of the instrument panel backlight variable panel in the data stream changes from off to on. This indicates that the body control module has executed the command for the instrument backlight output.

 

Troubleshooting: Removing the combination meter and inspecting it revealed that 10 of the 12 backlight bulbs had blown filaments.

Through the light wiring diagram, know the instrument backlight control principle: when the headlight switch is placed in the parking light position, the body control module of the J3-8 feet through the headlight switch iron, the body control module captured this state, through the J1-10 feet to make the parking light relay coil iron, to light up the exterior of the parking light. At the same time, a control element also outputs voltage to the combination instrument backlight bulb through pin J2-44, respectively, and outputs voltage to the traction control switch group, radio, air conditioning control panel, cigarette lighter, left front door and window switch, right front door and window switch, and the headliner control panel switch through pin J1-48. (Through the verification of the real vehicle, the left front door latch switch, right front door latch switch, and the combination instrument assembly spring Coil are powered by J1-48 feet, and there is no backlight bulb), the body control module through the J1-30 feet collected from the light changer light signal to control the size of the instrument backlight voltage, to realize the factory instrument backlight adjustable light and dark.

With the ignition off, disconnect the J1 connector from the body control module and connect a wire with a 20A fuse – one end to the positive battery terminal and one end to pin J1-48, and found that the backlighting of the traction control switch group, the radio, the air conditioning control panel, the cigarette lighter, the left front door/window switch, the right front door/window switch, and the headliner control panel switch all lit up.

Combination of instrumentation on the still intact two bulbs installed, disconnect the body control module J2 connector, the same with a 20A fuse with one end of the wire connected to the positive terminal of the battery, one end of the wire connected to the J2-44 feet, the results found that the fuse immediately blew will be combined with the instrumentation connector is disconnected, will be adjusted to the resistance of the multimeter block, a pen connected to the body control module J2-44 feet, the other pen connected to the steering column fixing bolt, measured the wire resistance (as shown in Figure 4) is 1.02 (multimeter pen itself has a resistance of 0.42). The wire resistance (shown in Figure 4) is 1.02 (the multimeter pen itself has a resistance of 0.42).

Upon inspection, the gray wire of the instrument backlight control and the internal iron beam of the dashboard were found to be hitched. After handling the wires, one end of the wire with a 20A fuse is connected to the battery stop pole, and one end is connected to the J2-44 pin of the body control module, it is found that the backlight bulb of the combination instrument can be lit.

Put the body control module connector back on, turned on the parking light switch, and found that the instrument backlight still couldn’t light up. Disconnect the J1 and J2 connectors, and measure J2-44 pins and J1-48 pins are not latched to the body. The body control module was removed from the car, and its decomposition, using a multimeter from J2-44 feet and J1-48 feet as a starting point for the control unit board to do measurements, and finally found that a control element on the circuit board, one of which has been burned off a pin, will be re-soldered to the pin, the instrument backlighting back to normal.

 

Faulty summary: This case is a combination of instrument backlight circuit lap instantaneous voltage is too large, resulting in a combination of instrument backlight bulb filament burned out, while the corresponding components on the circuit board to control the backlight pins are also burned out together. As for the combination of instrumentation after turning on the small lights, the meter needle light, combined instrument information display, and radio display dim, by looking at the wiring diagram, there is no corresponding pin alone control, which

should be from the CLASS2 data bus to get the parking lights on the information, the meter needle light control, and the display dimming control.

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