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Home >> Audi >> 1994 >> S4 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Modules, Motors, Relays & Solenoids >> Fuel Pump Relay Control Signal
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Fuel Pump Relay Control Signal

NOTE: All voltage and continuity tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated differently in testing procedures. For help with diagnostic testing. See WIRING DIAGRAMS .

The fuel pump relay is located in the central electric panel under the instrument cluster, on the left side.

  1. Remove fuel pump relay from central electric panel (relay position 6). See Figure.
  2. Switch ignition to ON position.
  3. Connect DVOM multimeter, in turn, between: Relay connector terminals No. 28 and 34 (check voltage) then relay connector terminals No. 32 and 34 (check voltage). See Figure. Readings must be approximately 12 volts each. If NO: Repair or replace wiring as necessary. See WIRING DIAGRAMS .
  4. Connect LED tester (US 1115) between terminals No. 28 and 29. See Figure.
  5. Switch ignition to ON position.
  6. LED tester must light up dimly, then become visibly brighter while cranking starter. If LED tester lights up dimly when ignition is switched ON, but does NOT become brighter while cranking starter. Replace Engine Control Module (ECM). See ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article.
  7. If LED tester does NOT light up. Check wiring, connect (VAG 1598) test box (using VAG 1598/5 adapter cable) only to harness connector of ECM. See CONNECTING VAG 1598 TEST BOX .
  8. Check continuity between: terminal No. 28 of relay position 6, and terminal No. 3 of test box. Resistance must be 1 ohm maximum. See Figure.
  9. If resistance is not correct, repair or replace wiring. If wiring is Okay but LED tester does NOT light up. Replace ECM. Reinstall circuit breakers S73, S75, S72 and fuse No. 17 (15-Amp). After replacement of ECM, see ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article.
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