1994 Audi S4FACTORY OEM SERVICE PROCEDURE

Power Circuits

NOTE: For additional information. Also, see ECM GROUND & VOLTAGE CHECK in SELF-DIAGNOSTICS article.
  1. Check ECM circuit breaker -S64- in electronics box. Position 3 (Red holder). See Figure.
  2. Connect (VAG 1598) test box to Engine Control Module (ECM) wiring harness using (VAG 1598/5) adaptor cable. See CONNECTING VAG 1598 TEST BOX . ECM is not connected.
  3. Connect LED Tester (US 1115) between socket 18 of test box (constant positive) and to ground terminals No. 10, 14, 19 and 24 one after another. See Figure.
  4. LED tester must light up each time. If LED tester does not light up, repair open circuit. See WIRING DIAGRAMS .
  5. Connect ECM to adapter cable (VAG 1598/5).
  6. Pull out injector valve circuit breaker S72. Position 2 (Brown holder). See Figure.
  7. Connect LED Tester between terminal No. 19 (ground) and socket 37 of test box. Switch ignition ON. LED tester must light up.
  8. If LED teseter does not light up, replace ECM. After replacement of ECM, see ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article. Reinstall injector valve circuit breaker S72.
  9. If YES: Operate starter for a few seconds.
  10. LED tester must light up when ignition is switched ON and while operating starter.
  11. If LED tester goes out when starter is operated, check injector valve circuit breaker S72, replace if necessary.
  12. Check wiring for continuity between terminal No. 37 and injector valve circuit breaker S72. See Figure. Also, See WIRING DIAGRAMS .
Factory Service Tools

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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.