Electromagnetic interference (EMI) can be predicted using finite element software. Here the EMI created by current-carrying wires within a simplified automobile is calculated. The two-dimensional AOS/MAGNETIC analysis software is used here, but three-dimensional analysis can also be performed. First a rectangular-shaped cavity is analyzed by finite elements to obtain resonant frequencies in close agreement with those of classical theory. Then analysis of a simplified typical vehicle shows that cavity resonance can occur in the 80 MHz to 170 MHz frequency range, which may therefore interfere with FM radios or with microprocessors.