1987 Audi 5000 CS, AutomaticFACTORY OEM SERVICE PROCEDURE

All Models

  1. Item Being Tested - Solenoid Valve Relay (On Position) With ignition on, place ABS tester in program switch position No. 2. Lamps No. 1 and 3 (Green) must come on. If lamp comes on, TEST 2 is completed. If lamp No. 4 (Red) comes on, replace defective solenoid valve relay and go to next step.
  2. Remove plug connector on hydraulic modulator. Connect voltmeter between terminal No. 4 on plug for hydraulic modulator and ground. Voltmeter reading should be about 12 volts. If reading is incorrect, repair wiring harness. If reading is correct, go to next step.
  3. Use ohmmeter to check continuity between contact No. 4 in socket on hydraulic modulator and terminal No. 87 in socket for solenoid valves. If there is no continuity, replace hydraulic modulator. If continuity exists, go to next step.
  4. Use ohmmeter to check continuity between terminal No. 6 in socket of hydraulic modulator and terminal No. 85 in socket for return pump relay. If there is no continuity, replace hydraulic modulator. If continuity exists, go to next step.
  5. Use ohmmeter to check continuity between terminal No. 86 in socket for solenoid valves and terminal No. 86 in socket for return pump relay. See Figure - Figure . If there is no continuity, replace hydraulic modulator. If continuity exists, go to next step.
  6. Use ohmmeter to check continuity between terminal No. 86 in socket for solenoid valves and terminal No. 2 in socket on hydraulic modulator. If there is no continuity, replace hydraulic modulator. If continuity exists, go to next step.
  7. Connect voltmeter between terminal No. 2 in plug for hydraulic modulator and ground. Voltmeter reading should be about 12 volts. If reading is incorrect, repair wiring harness. If reading is correct, go to next step.
  8. Turn ignition off. Use ohmmeter to check continuity between terminal No. 6 in plug for hydraulic modulator and terminal No. 27 in plug for ABS control unit. If there is no continuity, repair wiring harness to restore continuity.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.