A method of fault detection for use in a plasma processing chamber is provided. The method comprises monitoring plasma parameters within a plasma chamber with a single planar ion flux (PIF) probe, analyzing the resulting information, measuring the plasma parameters as a function of time and analyzing the resulting data. The data can be observed, characterized, compared with reference data, digitized, processed, or analyzed to reveal a specific fault. The PIF probe is preferably positioned at a grounded surface within the reactor. Chamber faults that can be detected include a build-up of process by-products in the process chamber, a helium leak, a match re-tuning event, a poor stabilization rate, and a loss of plasma confinement.