This paper presents a fault model for vehicle functions that includes communication devices for inter-vehicle cooperation. In particular, the fault model addresses vehicles where automation has partially replaced the driver, i.e., semi-automated cooperative vehicles. Components considered in the fault model include human drivers, communication systems, sensors, actuators, and control units. A description of faults in cooperative systems in general is complemented with an identification of errors in a platooning system. The identification has revealed systematic faults in software and human errors in the interaction between the system and the driver.