6.6L (LB7) Engine Vibration, Misfire, Rough Idle , and No DTCs - kw contaminated contamination diesel flywheel foaming fuel idle leak manual miss noise odor smoke vapor vent

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

6.6L (LB7) engine vibration, misfire, rough idle, and no DTCs.

1. Verify the engine has the correct oil level and check for presence of diesel fuel in the engine oil. If diesel fuel is found in the crankcase, complete SI diagnosis for fuel leaks inside of engine.
2. If DTCs are present, complete the SI diagnostic chart for the DTC found.
3. Use the Tech 2 to monitor the cylinder balance rates. If balance rates are excessive, complete The SI diagnostics for "Fuel Injector Balance Test with Tech 2".
4. Check for loose or missing torque convertor bolts.

NOTE: DO NOT RUN ENGINE WITH THE TRANSMISSION TORQUE CONVERTER REMOVED. THIS MAY SHEAR THE CRANKSHAFT BALANCER PIN.

5. Inspect the engine mounts and accessories for any ground out conditions.
6. Remove the accessory drive belt and evaluate the concern.
7. Remove the crankshaft balancer assembly and inspect for a possible sheared or damaged crankshaft balancer alignment pin. The crankshaft balancer assembly may rotate on the crankshaft and cause an engine out of balance condition. Verify the crankshaft balancer is torqued to the proper SI specification.
8. If the vehicle has a manual shift transmission, SI diagnosis is inconclusive, and the above suggestions do not lead to a repair suspect a Dual Mass Flywheel imbalance. A Dual Mass Flywheel imbalance can cause abnormal injector balance rates, excessive engine rattle noises, and excessive shift lever vibration. Replace the Dual Mass Flywheel as needed.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

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