2001 jeep cherokee rumble on 2001 Jeep Cherokee

I have a rumble sort of noise coming from behind the glove box. Its especially loud when the car is in idle. Anyone know what this could be?

Asked by for the 2001 Jeep Cherokee
There is a Technical Service Bulletin to address a concern that sound similar to your description. NUMBER: 18-016-01 GROUP: Vehicle Performance; DATE: July 13, 2001; 2000-2001 Cherokee with 4.0L Engine. SYMPTOM: Some customers may experience a boom-like sound when the engine is idling. This condition will normally only occur when the vehicle is stopped, the engine is at an idle, and when either the air conditioning or the defrost mode is selected. This condition may be caused by an exhaust system induced vibration into the vehicle body. This bulletin involves the installation of an exhaust pipe steady rest bracket and reprogramming the Powertrain Control Module (PCM) with new software (calibration level 2001 XJ - Calibration Level15B or 2000 XJ - Calibration Level 15C).