Hi, the ABS light is controlled by the ABS module. If the bulb is not lighting up there may be a fault with the module or the bulb is bad or there is a fault with the wiring or the instrument cluster. This will not cause the rear brakes not to function. If the rear brakes are not functioning there may be a fault with the brake master cylinder or the ABS modulator or with the rear calipers or hoses. The ABS light function is not directly tied into the rear brake function.
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No, the module is locate in the module box located at the right rear of the engine compartment. You will need to remove the water collector and the top cover of the module box to access the modules. The modulator is located at the left front of the engine compartment. Just follow the brake lines from the brake master cylinder over to the modulator.
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