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Home >> BMW >> 1994 >> 740iL >> Repair and Diagnosis >> Brakes >> Traction Control >> Anti-Lock/Traction Control >> Diagnosis & Testing >> Test 8 - Abs Return Flow Pump
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Test 8 - Abs Return Flow Pump

NOTE: This test requires a brake dynamometer. See TESTING ON BRAKE DYNAMOMETER  .
  1. Connect "T" plug with adapter "A" to ABS wiring harness connector. Connect "T" plug with adapter "B" to ECU. Connect service tester lead to adapter "A". Red light should come on.
  2. Place front axle on dynamometer. Ensure tester is flashing FRONT LEFT. Turn ignition on. Check voltage between leads No. 1 and 10. Voltage should be greater than 11.5 volts. If necessary, idle engine. Turn dynamometer on.
    3. NOTE: Slight pressure will be felt on brake pedal when pump starts.
  3. Apply brakes until dynamometer reading is about 450 lbs. (204 kg), and charge axle if necessary. Maintain a steady pedal force. Press ABS test button. After about 5 seconds, valve will cut in briefly. After about 4 seconds, pressure pump cuts in briefly after COMPLETED display appears and brake dynamometer reading drops again. After about 3 seconds, end test by pressing test button again.
  4. Repeat test on right front, left rear and right rear wheels. If nominal values are not reached, check battery voltage and hydraulic unit. Check for cross-connected brakelines on hydraulic unit. Replace hydraulic unit if necessary.
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