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Home >> GMC >> 1998 >> Forward Control 6.5 F >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing - 6.5L Turbo Diesel >> Fuel System >> Water In Fuel Light Diagnosis
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Water In Fuel Light Diagnosis

  1. Turn ignition switch to RUN position. If water in fuel light does not illuminate, go to next step. If water in fuel light illuminates briefly, go to step 5).
  2. Disconnect water in fuel sensor harness connector. Ensure ignition switch is in RUN position. Using a test light connected to ground, probe ignition feed circuit (Pink wire) at water in fuel sensor harness connector. See Fig 1. If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
  3. Connect a test light between ignition feed circuit (Pink wire) and ground circuit (Black wire) at water in fuel sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  4. Using a test light connected to ground, probe indicator light control circuit (Yellow/Black wire) at water in fuel harness connector. If test light does not illuminate, go to step 8). If test light illuminates, replace water in fuel sensor.
  5. Check for poor connection at water in fuel sensor and instrument cluster. If problem exists, repair as necessary. If problem does not exist, system is functioning properly at this time.
  6. Repair open in ignition feed circuit (Pink wire) for open, between ENG 1 fuse and water in fuel sensor harness connector.
  7. Repair open in ground circuit (Black wire).
  8. Check indicator light control circuit (Yellow/Black wire) for open, between instrument cluster and water in fuel sensor harness connector. If open does not exist, go to next step. If open exists, repair as necessary.
  9. Check for blown GAUGES fuse. If fuse is blown, repair short to ground in ignition feed circuit (Pink wire) between GAUGES fuse and instrument cluster harness connector. If fuse is not blown, go to next step.
  10. Check for power to GAUGES fuse. If power exist, go to next step. If power does not exist, repair as necessary.
  11. Check indicator light ignition feed circuit (Pink wire) for open, between GAUGES fuse and instrument cluster harness connector. If open exists, repair as necessary. If open does not exist, go to next step.
  12. Repair or replace instrument cluster and/or replace water in fuel indicator light bulb as necessary.
Fig 1: Identifying Water In Fuel Sensor Harness Connector Terminals
G98D00870Courtesy of GENERAL MOTORS CORP.
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