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 MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 2369 (ENGINE CONTROLS AND FUEL - 3.6L - DTC P0201 TO DTC P0629)DTC P0300-P0306 (LLT)CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Circuit/System Testing
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2010 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
- 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 .
- Exhaust system restrictions
- If you find any of the above conditions, repair as necessary.
- Ignition OFF, remove the T8 ignition coil of the misfiring cylinder, but leave 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.
- Install the J 26792: Spark Tester to the boot of the appropriate T8 ignition coil and ground.
- Attempt to start the engine and observe the J 26792:
Spark Tester. 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 suspected spark plug with another cylinder that is operating correctly.
- 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 Q17 fuel injector-Refer to Fuel Injector Solenoid Coil Test (LLT) .
- 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.