1988 Audi 5000 CS, StandardFACTORY OEM SERVICE PROCEDURE

Differential Pressure Regulator

  1. Using Adapter (VW 1315 A/1), connect multimeter to differential pressure regulator. Set multimeter to 200 mA DC scale. Insert fuse in top of fuel pump relay. Turn ignition on. Remove fuse after 4 seconds.
  2. Indicator light should display Code 4341. Multimeter should read 100 mA. Close full throttle switch. Multimeter reading should change to 10 mA. If no reading is shown, disconnect harness connector from differential pressure regulator.
  3. Connect multimeter between terminal No. 2 of harness connector and engine ground. See Fig 1 . Turn ignition on. Multimeter should read 4.5-5.0 volts.
  4. Connect multimeter between terminal No. 1 and terminal No. 2 of harness connector. Multimeter should read 4.5-5.0 volts. If specification is obtained, replace differential pressure regulator.
    Fig 1: O2 Sensor & Differential Pressure Regulator Connector
    G94344Courtesy of AUDI OF AMERICA, INC.
  5. If specification is not obtained, remove FICU access cover and disconnect harness connector. Using multimeter, check for continuity between FICU connector terminal No. 4 and differential pressure regulator connector terminal No. 1.
  6. Check for continuity between FICU connector terminal No. 5 and differential pressure regulator connector terminal No. 2. Resistance reading should be .2 ohm for both tests.
  7. If specification is not obtained, repair break in wiring. If specification is obtained, replace FICU.
Fig 2: View of FICU Harness Connector
G94345Courtesy 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.