Drive Belt Chrip When the Engine is Shut Off - keywords 6.6 accessory alternator engine generator LBZ LLY noise off pulley squeak wear

The PI was revised to include information on dual alternator systems. Please discard PIP3772A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

The customer concern will be a accessory drive belt chirp when the engine is shut off. Belt chirp when the engine is shut off has always been a characteristic of the diesel engine. The belt chirp is caused by the high engine compression and the rapid stopping of the crankshaft. Due to a larger/higher output alternator, the belt chirp on a 2006 diesel engine equipped vehicle may be slightly louder than a older model vehicle. Some 2006 diesel engines may already have a clutched alternator pulley to reduce the amount of belt chirp when the engine is shut off.

If a 2006 diesel engine equipped (LBZ or LLY) vehicle has come to the dealer with a customer concern of a belt chirp when the engine is shut off, and the vehicle does not have a clutched alternator, a clutched alternator can be installed to reduce or eliminate the shut off noise. No special part number or ordering is needed. If the current part number for a new alternator is ordered from GMSPO, a clutched alternator will be shipped.

Note: The clutched pulley alternator is only used on single alternator systems. If the vehicle is equipped with a dual alternator system (RPO code 8X5), the clutched alternator cannot be used.

Please follow this diagnostic or repair 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.