SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 250 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING - 6.6L)FUEL SYSTEMSFUEL HEATER INOPERATIVEDIAGNOSTIC PROCEDURES
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedures

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION 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 .
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.