1990 Audi 100 Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Auto Check System Code Verification Test

NOTE: The Code Verification test can only be done when the vehicle is not moving.
  1. Push and hold the Auto-Check button, switch ignition on and read code displayed. This display should read 4 or 5 depending on number of engine cylinders, and 1-6 for the country variation. See AUTO-CHECK SYSTEM CODE table. If the code is not correct, turn engine off. Remove instrument cluster, leaving connectors attached. Slide code switch on back of instrument cluster, to appropriate code setting. See Fig 1 .
    AUTO-CHECK SYSTEM CODE

    Switch position Country Variation Engine
    1 German speaking Gas
    2 USA Gas
    3 Non-German speaking Gas
    4 German speaking Diesel
    5 USA Diesel
    6 Non-German speaking Diesel
    Fig 1: Auto-Check System Code Switch
    G91A02080Courtesy of AUDI OF AMERICA, INC.
  2. If the code for the number of cylinders does not match the engine in the vehicle. Remove the 26 terminal electrical connector (Yellow) from the Auto-Check system and attach to (VW 1594/16) Test Harness Connector. See Fig 2 .
  3. Connect ohmmeter between contact No. 3 and engine ground. On 4-cylinder vehicles, ohmmeter should read infinite ohms. On 5-cylinder vehicles, ohmmeter should read 0.0 ohms. If specified value is not correct, repair short or open circuit.
  4. If specified value is correct but proper coding is still not displayed, check voltage supply and output signals. If code is still not correct, replace Auto-Check module.
Fig 2: Test harness (VW 1594/16) Terminal Identification.
G91E02082Courtesy of AUDI OF AMERICA, INC.
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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.