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Anti-lock Brake Systems ABS

Anti-lock Brake Systems ABS. R. Bortignon. ABS. designed to control wheel lock-up to minimize stopping distance & help maintain steering control is also used on vehicles with air brakes. ABS Components. How Many Channels?.

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Anti-lock Brake Systems ABS

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  1. Anti-lock Brake SystemsABS R. Bortignon

  2. ABS • designed to control wheel lock-up to minimize stopping distance & help maintain steering control • is also used on vehicles with air brakes

  3. ABS Components

  4. How Many Channels? • a channel describes a brake hydraulic line that is capable of being controlled by the ABS

  5. Wheel Speed Sensor • wheel speed sensor is a magnetic impulse sensor • works like a crankshaft position sensor • creates an AC voltage signal as the tone ring rotates with the wheel • the AC voltage signal frequency changes as the wheel speed changes

  6. Modulating Brake Fluid Pressure • EBCM activated solenoids modulate brake fluid pressure • these solenoid valves can either… • hold (maintain) pressure • dump (release) pressure • increase pressure • these solenoids can cycle the brakes 15 times/second Hold Pressure Dump Pressure Increase Pressure

  7. Electronic Brake Control Module (EBCM)

  8. ABS “Electro-Hydraulic” Modulator • may be attached to the master cylinder • integral ABS • may be mounted separate from the master cylinder • non-integral ABS

  9. Servicing Precautions • Bleeding • may be done exactly the same as a non-ABS equipped vehicle • or may have specific bleeding procedures • when disconnecting brake lines, accumulator pressure may have to be relieved – can be up to 2800 PSI! • read manufacturer's instructions carefully before beginning repairs! • ABS problem: always begin with a thorough inspection of the base brake system (non-ABS portion) first • brake warning light indicates a problem in the base braking system – not the ABS • ABS warning lamp indicates a problem within the ABS

  10. Warning Lights • both brake warning lights should come on when the ignition is turned on • this confirms that the warning circuit is operational

  11. Service Tips • check wheel speed sensors for debris build-up • check tone rings for damage/debris • check sensor wiring & connectors • mismatched tire sizes confuses EBCM

  12. Service Tips • do NOT push caliper pistons in without loosening bleeder screw • this prevents dirt from being pushed out of the caliper & into the modulator • regular brake fluid flushes (every 2 years) minimize modulator & solenoid problems & extends their life span

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