GMC Yukon 2000–2006

From the manufacturer’s document

• Applies to：The model list names GMC Yukon models, 2002 - 2014, with a V8 engine.
• Condition：With the SES light on, a P0300-P0308 DTC is found with misfires counting on a single cylinder that may or may not be felt.
• Condition：A verified noise is not eliminated by canceling fuel injectors and occurs at camshaft speed (half of crankshaft speed); it may be a chirp, squeak, squeal or tick and may increase off idle.
• Cause：When SI diagnosis does not isolate the cause, it may be a worn camshaft lobe and/or lifter roller, a sticking valve, valve leakage, a broken valve spring, or a collapsed AFM (Active Fuel Management) lifter.
• Confirm：During the noise, press with a wooden hammer handle on the valve side, push rod side and side of each rocker arm; if pressure on the valve side changes the noise, it is most likely a lifter and/or cam lobe concern on that cylinder.
• Confirm：Measure cam lobe lift at the push rod side of the rocker arm and compare with other rockers on the same bank; the misfiring or ticking cylinder should have clearly less lift if a lifter roller and/or cam lobe is worn.
• Confirm：A good indicator of a sticking valve is misfires that continue to count on an aggressive deceleration with engine braking.
• Confirm：For a suspected sticking valve, snap the valve onto its seat and confirm it comes off easily; if force is needed to tap it off the seat, excessive carbon build up exists, which may be repaired by decarboning the engine.
• Confirm：The Cylinder Leakage Test outlined in SI should isolate valve leakage by finding excessive leakage past an intake or exhaust valve compared with the others.
• Confirm：A broken valve spring may stay stacked together and be hard to see, so lightly push on different places on the springs with a small hammer handle.
• Repair：If a worn camshaft lobe or lifter roller is found, replace the camshaft and all lifters per SI, and also replace the plastic lifter guide for the lifter that had the damage.
• Caution：A worn cam lobe is easy to overlook through the lifter bores, and unworn lifter rollers do not mean the related cam lobes are okay; both must be carefully inspected.
• Caution：If an AFM lifter concern is suspected, refer to the latest version of PIP4568 for additional information.

From the manufacturer’s document

• Applies to：Applies to 2023 and prior GM passenger cars and trucks, including medium duty trucks and excluding LCF medium duty trucks.
• Condition：Exterior lamps such as cornering, turn signal, backup, head or tail lamps may show very small water droplets, a fine mist or white fog (condensation) on the inside of the lens.
• Cause：Condensation occurs when the air inside the lamp assembly reaches the dew point through atmospheric changes.
• Caution：Depending on the lamp and the atmospheric conditions, the time needed to clear the lamp may vary from 2 to 6 hours.
• Confirm：Normal: the mist is located mainly in the lens corners near the vents and does not cover more than half the lens surface.
• Confirm：Normal: the moisture clears when the vehicle is parked in a dry environment or driven with the lights on.
• Caution：If the normal conditions are noted, advise the customer that replacing the lamp assembly may not correct the condition.
• Repair：A condition covering more than half the surface of the lamp lens indicates the need to service the lens or lamp assembly.
• Confirm：Leak: water has accumulated in the bottom of the lamp assembly.
• Confirm：Leak: the condition will not clear when the vehicle is parked in a dry environment or driven with the lights on.
• Caution：Moisture that "comes and goes" is considered a normal condition.
• Cause：Non-OE lamps are most often presented as holding moisture or with inoperative bulbs from corroded electrical connections; they appear to be installed as part of a collision repair.