OTC Tools OTC 7957 Ford Villager Air Bag Simulator. Servicing the self-diagnostic air bag systems is required in different circumstances. In the self-diagnostic system, an "AIR BAG" readiness lamp will flash a trouble code if the system is faulty, whenever the air bag is deployed, whenever a car is being scrapped, or when other repairs are needed on the steering column and the air bag module must be removed. Diagnosis of air bag system faults is impossible without these tools because the circuit remains open. These tools are essential for body shops. Some diagnostic procedures require the use of one of these special air bag simulators. In effect, they simulate a complete circuit for diagnostic purposes. Each is used in the same way. With the power disconnected and drained from the air bag backup system, the module is removed and disconnected. The air bag simulator gets plugged into the vehicle harness connector and power is restored. Special three ohm resistor for use on air bags on Villager vehicles.