| Subject: | Buzz or Hum Noise From Headliner Above Driver |
| Models: | 2002-2008 Cadillac Escalade, EXT, ESV |
| 2000-2008 Chevrolet Avalanche, Suburban, Tahoe |
| 2003-2008 Chevrolet Silverado, Silverado Classic |
| 2003-2008 GMC Sierra, Sierra Classic |
| 2000-2008 GMC Yukon, Yukon XL, Yukon Denali, Yukon Denali XL |
This PI was superceded to update Model Years. Please discard PIT3511A.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Customers may comment that they have a buzz/vibration/hum noise emanating from the headliner in an area that looks like a microphone or a small speaker.
Recommendation/Instructions:
The plastic escutcheon grill, which is round and located just above the driver to the left, is the interior ambient temperature sensor. The sensor is used in conjunction with the automatic HVAC (CJ2 or C68). On occasions, this sensor has been known to
make a buzz/vibration/hum sound. The sensor uses a small fan to pull air over the sensor. This noise may be intermittent.
Although it may not be possible to alleviate all of the noise, Engineering has found that if the sensor is installed incorrectly that it may bind and cause the fan to make noise. Remove the sensor and while doing so check for any binding. Reinstall the
sensor and re-test. If the noise is still present, the sensor itself may be noisy and require replacement.
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.
