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Home >> Audi >> 1994 >> S4 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Engine Sensors & Switches >> Vehicle Speed Sensor Checking >> Perform Test Drive
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Perform Test Drive

  1. Select "READ MEASURING VALUE BLOCK" function 08 using (VAG 1551) Scan Tool and input display group number 04. See READING/MEASURING VALUE BLOCK (FUNCTION 08) under OUTPUT DIAGNOSTIC TEST MODES (DTM) in SELF-DIAGNOSTICS article.
  2. Observe display value in channel 3.
  3. Vehicle at stand-still: Speed must always be 2.5 MPH.
  4. Vehicle exceeding 2.5 MPH: Speed value must be displayed.
  5. If speed value is absent: Raise left front wheel off ground.
  6. Connect (VAG 1598) test box, using (VAG 1598/5) adapter cable, to ECM. See CONNECTING VAG 1598 TEST BOX .
  7. Connect (US 1115) LED tester between terminal No. 18 (positive) and terminal No. 50 (signal). Switch ignition ON.
  8. Slowly rotate left wheel by hand. LED tester must blink momentarily. If LED does not blink, switch ignition OFF.
  9. Wait at least 30 seconds before disconnecting adapter cable from ECM.
  10. Switch ignition ON.
  11. Slowly rotate left front wheel by hand. LED tester must blink momentarily.
  12. If LED blinks, replace ECM. After replacement of ECM, see ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article.
  13. If LED does not blink, check for open/short circuit in wiring between ECM connector terminal No. 50 (test box terminal 50), and instrument cluster. See Figure. See WIRING DIAGRAMS .
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