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Marty, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 54827
Experience:  Bosch Certified Master Technician with over 35 years experience in the automotive industry.
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W140 1992 400sel abs light NOT illuminating when ignition

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W140 1992 400sel abs light NOT illuminating when ignition key turned on before starting engine , all other warning lights are on and go off after starting as normal. Also rear brakes not working. Alternator is working ok as engine does not cut off when battery cable is removed. Is there a connection between the no abs light and the rear brakes not working.

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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Customer: replied 1 year ago.
Is the abs module and the abs modulator the same thing and where are they located in the engine compartment

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.

Let me know if you need anything else.


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