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Home >> Cadillac >> 2002 >> Escalade EXT >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Fuel System (Diesel) >> Fuel Heater Inoperative Diagnosis (6.6L) >> Diagnostic Procedure
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Diagnostic Procedure

  1. Does Water In Fuel light operate properly? If yes, go to next step. If no, go to WATER-IN-FUEL LIGHT ALWAYS ON (6.6L)  or WATER-IN-FUEL LIGHT INOPERATIVE (6.6L) 
  2. Disconnect fuel heater harness connector from top of fuel filter/heater element housing. Turn ON the ignition with the engine OFF. Probe fuel heater Ignition 1 voltage circuit with test light connected to a good ground. Does test light illuminate? If yes, go to next step. If no, go to step  5.
  3. Probe fuel heater ground circuit at fuel filter/heater element housing with test light connected to battery voltage. Does test light illuminate? If yes, go to next step. If no, go to step  10.
  4. Remove fuel filter from fuel filter/heater element housing. Test Ignition 1 voltage circuit and ground circuit for an open in fuel filter/heater element housing. Did either circuit test open? If yes, go to step  11. If no, go to step  7.
  5. Is fuel HT fuse open? If yes, go to next step. If no, go to step  8.
  6. Disconnect intake air heater harness connector. Probe Ignition 1 voltage circuit with test light connected to battery voltage. Does test light illuminate? If yes, go to step  9. If no, go to next step.
  7. Remove fuel filter/heater element housing from vehicle. On a bench, cool sensor part of fuel heater with ice. With fuel heater below 46°F (8°C), wet heating element with fuel. Connect Ignition 1 voltage circuit of fuel heater to battery voltage and connect ground circuit of fuel heater to ground on top of housing. Observe heating element. Does heat occur? If yes, go to step  13. If no, go to step  12.
  8. Repair open in Ignition 1 voltage circuit between fuel filter/heater element housing and HT fuse. After repairs, go to step  14.
  9. Repair short to ground on Ignition 1 voltage circuit. After repairs, go to step  14.
  10. Repair open in ground circuit between fuel filter/heater element housing and chassis ground. After repairs, go to step  14.
  11. Replace fuel filter/heater element housing. After repairs, go to step  14.
  12. Replace fuel heater. After repairs, go to step  14.
  13. Replace intake air heater relay. After repairs, go to step  14.
  14. Operate vehicle under which problem was noted. Does system operate properly? If yes, system is okay. If no, go to step  1.
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