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Home >> Audi >> 1994 >> S4 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Emission Systems & Sub-Systems >> EVAP Canister Purge Regulator Checking >> Checking Control Signal
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Checking Control Signal

  1. Disconnect EVAP canister purge regulator valve harness connector.
  2. Connect (US 1115 LED) tester (using VW 1594 connector test kit), between terminal No. 2 of EVAP canister purge regulator valve harness, and engine ground. See Figure.
  3. Operate starter for a few seconds. LED tester must light up.
  4. If NO: Check the following items in the electronics box and repair as necessary:
    • Injector valve circuit breaker S72 okay.
    • EVAP frequency valve circuit breaker S75 okay.
  5. Check continuity between terminal No. 2 of EVAP canister purge regulator valve harness, and EVAP frequency valve circuit breaker S75. Resistance must be 0.5 ohm maximum.
  6. Check continuity between EVAP frequency valve circuit breaker S75, and terminal No. 31 of fuel pump relay -J17-, relay position 6. See Figure. Resistance must be 0.5 ohm maximum.
  7. Check control signal to fuel pump relay. See FUEL PUMP RELAY CONTROL SIGNAL .
  8. Reconnect LED tester, between terminal No. 2 of EVAP canister purge regulator valve harness, and engine ground. See Figure.
  9. Initiate Output Diagnostic Test Mode (DTM). See OUTPUT DIAGNOSTIC TEST MODE (DTM) in SELF-DIAGNOSTICS article. LED tester must light up.
    NOTE: Positive (+) voltage must be available at terminal No. 2 of harness connector regardless of which Output DTM is called up.
  10. If LED tester does NOT light up, connect (VAG 1598) test box, using (VAG 1598/5) adapter cable to ECM. See CONNECTING VAG 1598 TEST BOX . ECM remains disconnected.
  11. Check continuity between terminal No. 2 of EVAP canister purge regulator valve harness connector, and test box terminal 37, using wiring diagram. Resistance must be 0.5 ohm maximum. See WIRING DIAGRAMS .
  12. If circuit is open: Repair wiring between terminal No. 37 of ECM connector, and terminal No. 2 of EVAP canister purge regulator valve connector. See Figure.
  13. If continuity is OK, replace ECM. After replacement of ECM, see ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article.
  14. Remove test box and adapter cable. Reconnect ECM to vehicle wiring harness.
  15. Connect LED tester to terminals No. 1 and 2 of EVAP canister purge regulator valve harness connector.
  16. Initiate Output Diagnostic Test Mode (DTM). See OUTPUT DIAGNOSTIC TEST MODE (DTM) in SELF-DIAGNOSTICS article. LED tester must blink when valve is activated.
  17. If LED tester does not blink, connect (VAG 1598) test box, using (VAG 1598/5) adapter cable to ECM. See CONNECTING VAG 1598 TEST BOX . ECM remains disconnected.
  18. If LED tester lights up continuously: Check wiring (using wiring diagram) between terminal No. 1 of EVAP canister purge regulator valve harness and test box terminal 5 for short circuit to ground. See WIRING DIAGRAMS .
  19. If LED tester does NOT blink: Check continuity between terminal No. 1 of EVAP canister purge regulator valve harness connector, and test box terminal 5. Resistance must be 1.0 ohm maximum.
  20. If circuit is grounded or open between terminal No. 1 of EVAP canister purge regulator valve connector, and terminal 5 of ECM connector. See Figure. Repair as necessary.
  21. If circuit is OK: Replace ECM. See ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article.

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