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HOMESERVICE MANUALSAUDI199590 BASE, 2.8 K, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - SYSTEM/COMPONENT TESTSFUEL SYSTEMFUEL DELIVERYFUEL PUMP RELAY USING SCAN TESTER
1995 Audi 90 Base, 2.8 K, Automatic

Fuel Pump Relay Using Scan Tester

1995 Audi 90 Base, 2.8 K, AutomaticSECTION Fuel Pump Relay Using Scan Tester
  1. Remove fuse No. 13. See the ELECTRICAL COMPONENT LOCATIONS  . Using jumper wire from Adaptor Kit (VW 1594), connect LED Tester (VAG 1527B) between chassis ground and rear terminal of fuse No. 13 receptacle.
  2. Initiate OUTPUT DTM. See TESTS W/CODES article. In output DTM, activate fuel pump relay. Fuel pump relay should click and LED should come on. If fuel pump relay does not click, go to step 6). If fuel pump relay clicks but LED does not come on, remove fuel pump relay. Check for faulty wiring between fuse No. 13 and terminal No. 52 of fuel pump relay connector. See Fig 1 .
  3. If wiring is okay, install fuel pump relay and fuse No. 13. Remove fuse No. 28. Connect LED tester between chassis ground and either terminal of fuse No. 28 receptacle.
  4. In output DTM, activate fuel pump relay. Fuel pump relay should click and LED should come on. If fuel pump relay does not click, go to step 6). If fuel pump relay clicks but LED does not come on, connect LED tester between chassis ground and other terminal of fuse No. 28 receptacle.
  5. In output DTM, activate fuel pump relay. If LED still does not come on, remove fuel pump relay. Check wiring between fuse No. 28 and terminal No. 59 of fuel pump relay connector. If wiring is faulty, repair or replace wiring as necessary. If wiring is okay, replace fuel pump relay.
  6. Turn ignition off. Remove fuel pump relay. Turn ignition on. Check voltage between relay connector terminals No. 46 and 50, and terminals No. 48 and 50. See Fig 1 .
  7. If battery voltage is not present across both sets of terminals, repair wiring. If battery voltage is present across both sets of terminals, connect LED tester between terminals No. 46 and 47. When ignition is turned on, LED should come on brightly for about one second, then become dim and stay dim. When starter is engaged, LED should become distinctly brighter.
  8. If LED comes on, replace fuel pump relay. If LED does not come on, use Adaptor Cable (1598/12) to connect Test Box (VAG 1598) to Electronic Control Module (PCM) wiring harness connector. Leave PCM disconnected.
  9. Measure resistance between relay connector terminal No. 47 and test box terminal No. 15. If resistance is more than one ohm, repair wiring as necessary. If resistance is less than one ohm, replace PCM.
Fig 1: Locating Fuel Pump Relay & Identifying Terminals (90)
G93B80995Courtesy of AUDI OF AMERICA, INC.
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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.
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