A method of assigning faults to a processing chamber is described. Some embodiments include applying a radio frequency (RF) signal to a processing chamber to stimulate resonance in the chamber, measuring resonances of the applied RF signal in the chamber, extracting a fingerprint from the measured resonances, comparing the extracted fingerprint to a library of fingerprints, assigning a similarity index to combinations of the extracted fingerprint with at least one fingerprint in the fingerprint library, comparing each similarity index to a threshold, and if the similarity is greater than a threshold, then assigning a fault to the processing chamber using the library fingerprint.