Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1938 (ENGINE CONTROLS AND FUEL - 3.6L (LCS) - DTC P0192 TO DTC P0629)DTC P0300-P0306CIRCUIT/SYSTEM TESTING
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Circuit/System Testing
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, open the hood to disable the Auto-Stop function.
- Ignition ON, verify the scan tool hood position parameter displays Open.
- If the hood position does not display Open, refer to DTC P254F .
- Verify that the following conditions do not exist:
- Vacuum hose splits, kinks, and incorrect connections
- Engine vacuum leaks
- Crankcase ventilation system for vacuum leaks
- Fuel pressure that is too low or too high-Refer to Fuel System Diagnosis
- Contaminated Fuel-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool)
- Exhaust system restrictions
- If you find any of the above conditions, repair as necessary.
- Ignition OFF, remove the ignition coil of the misfiring cylinder, with the electrical connector connected.
- Inspect the ignition coil boot for the following conditions:
- holes
- tears
- carbon tracking
- oil contamination
- water intrusion
- If you find any of the above conditions, repair as necessary.
- Remove the fuse that supplies voltage to terminal 32 of the fuel pump control module (FPCM).
- Install the J 26792 to the boot of the appropriate ignition coil and ground.
- Attempt to start the engine and observe the J 26792
. The spark tester should spark.
- If there is no spark, refer to Electronic Ignition System Diagnosis for diagnosis of the ignition coil.
- Ignition OFF, remove the spark plug from the misfiring cylinder. Verify that the spark plug does not exhibit the following conditions:
- Gas, coolant, or oil fouled-Refer to Spark Plug Inspection .
- Cracked, worn, incorrectly gapped-Refer to Ignition System Specifications .
- If there is a condition with the spark plug, replace the spark plug.
- Exchange the spark plug with another cylinder that is operating correctly.
- Install the fuse that supplies voltage to terminal 32 of the fuel pump control module (FPCM).
- Engine idling, observe the scan tool Misfire Current Counter parameters. The misfire should not follow the spark plug exchange.
- If the misfire follows the spark plug, replace the spark plug.
- If all conditions test normal, test or inspect for the following:
- A lean or rich fuel injector-Refer to Fuel Injector Solenoid Coil Test
- An engine mechanical condition-Refer to Symptoms - Engine Mechanical .
NOTE:
An erratic or weak spark is considered a no spark condition.
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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.