| Subject: | Buzz/Rattle Noise At 40-45 MPH or 1100-1300 RPM |
| Models: | 2007-2008 Cadillac Escalade, ESV, EXT |
| 2007-2008 Chevrolet Avalanche, Silverado, Suburban, Tahoe |
| 2007-2008 GMC Sierra, Yukon, Yukon Denali, Yukon XL, Yukon Denali XL |
| With Engine RPO L76, L92, LC9, LH6, LMG, LY2 or LY5 |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may comment on a buzz and/or rattle noise that will occur at 40-45 mph and/or 1100-1300 rpm just prior to the V4 to V8 transition. The noise will sound as though it's coming from within the IP. The cause may be the generator b+ cable miss
routed on the outboard side of the engine oil dipstick tube as seen below. At 1200 rpm in V4 mode (AFM) the engine oil dipstick goes into resonance and vibrates against the generator cable which produces a rattle noise in the vehicle.
Recommendation/Instructions:
To correct this concern re-route the generator b+ cable on the inboard side of the engine oil dipstick as seen below. Make sure the generator cable has at least 15 mm of clearance to the engine oil dipstick tube.
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.
