Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1987 Audi 5000 CS, StandardFACTORY OEM SERVICE PROCEDURE
All Models
- Item Being Tested - Return Pump Relay (Off Position) With ignition on, place ABS tester in program switch position No. 4. When button No. 5 lights up, press button. Lamps No. 1 and 3 (Green) must come on and return pump must run. If lamp comes on and pump runs, TEST 4 is completed.
- If lamp No. 4 (Red) comes on, replace defective return pump relay. After replacing relay, turn ignition off and remove plug connector from hydraulic modulator.
- Use ohmmeter to test continuity between terminal No. 11 in socket on hydraulic modulator and terminal No. 85 in relay socket for return pump. See Figure - Figure . If there is no continuity, replace hydraulic modulator. If continuity exists, go to next step.
- Use ohmmeter to check continuity between terminal No. 13 in socket on hydraulic modulator and terminal No. 87 in relay socket for return pump. If there is no continuity, replace hydraulic modulator. If continuity exists, go to next step.
- Turn ignition on. Connect voltmeter between terminal No. 13 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.
- Turn ignition off. Use ohmmeter to check continuity between terminal No. 11 in plug for hydraulic modulator and terminal No. 28 on plug for ABS control unit. If there is no continuity, repair wiring harness to restore continuity.
NOTE:
If all test results are correct but the return pump does not run when button No. 5 is pressed, replace hydraulic modulator.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.
