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Home >> Cadillac >> 2007 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 51 (Engine Controls - System & Component Testing - 6.6L) >> Fuel Systems >> Fuel Heater Inoperative >> Diagnostic Procedures
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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Is the WATER IN FUEL light operating properly? If yes, go to next step. If no, diagnose warning light.
  2. Turn ignition off. Disconnect the fuel heater harness connector from the top of the fuel filter/heater element housing. Turn ignition on, with engine off. Using a test light connected to ground, probe the fuel heater ignition 1 voltage circuit. Does the test light illuminate? If yes, go to next step. If no, go to step  5 .
  3. Using test light connected to battery voltage, probe the fuel heater ground circuit at the fuel filter/heater element housing. Does the test light illuminate? If yes, go to next step. If no, go to step  10 .
  4. Remove fuel filter from the fuel filter/heater element housing, mounted on valve cover. Test the ignition 1 voltage circuit and ground circuit for an open in the fuel filter/heater element housing. Did either circuit test open? If yes, go to step  11 . If no, go to step  7 .
  5. Is the fuel HT fuse open? If yes, go to next step. If no, go to step  8 .
  6. Disconnect the intake air heater harness connector. Probe the ignition 1 voltage circuit with a test light connected to battery voltage. Does the test light illuminate? If yes, go to step  9 . If no, go to next step.
  7. Remove the fuel filter/heater element housing from vehicle. On a bench, cool the sensor part of the fuel heater with ice. With the fuel heater below 46°F (8°C), wet the heating element with fuel. Connect ignition 1 voltage circuit of the fuel heater to battery voltage and connect ground circuit of the fuel heater to ground on the top of the housing. Observe the heating element. Does heat occur? If yes, go to step  13 . If no, go to step  12 .
  8. Repair open in the ignition 1 voltage circuit between the fuel filter/heater element housing and fuse. Did you complete the repair? If yes, go to step  14 .
  9. Repair short to ground on the ignition 1 voltage circuit. After repairs, go to step  14 .
  10. Repair open in the ground circuit between the fuel filter/heater element housing and chassis ground. After repairs, go to step  14 .
  11. Replace fuel filter/heater element housing. After replacing fuel filter/heater element housing, go to step  14 .
  12. Replace fuel heater. Fuel heater is located on fuel filter/heater element housing and is mounted on valve cover. After replacing fuel heater, go to step  14 .
  13. Replace intake air heater relay. Relay is located in glow plug controller housing, on upper intake manifold. After replacing relay, go to next step.
  14. Operate vehicle under which the problem was noted. Does the system operate properly? If yes, system is okay. If no, go to step  1 .
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