Most drivers think of the ignition switch as the slot where they insert the key to start their car, but that’s actually the ignition lock cylinder. The ignition switch is a more complex electrical component that has to “read” anti-theft coding in the key before it will activate electrical systems in the vehicle so the vehicle can start or allow an automatic transmission to be shifted out of Park.
On vehicles with push-button start, the ignition switch has to recognize the anti-theft code transmitted by the key fob before it will allow the engine to start.
If nothing happens when the key is turned in the ignition lock or no dashboard lights come on when it’s turned to the on position, those are signs that an ignition switch has failed or there’s a problem with the wiring from the switch to the starter or other electrical components. Those could also be signs of other problems, such as a failed starter motor or a dead battery.
Another potential issue is that a heavy key ring can cause wear on the lock cylinder and the ignition switch, allowing the switch to turn to the off position when a car hits a bump or pothole, disabling the power-steering, air bags and other systems.
Electronic ignition systems still rely on some moving parts, such as a device to distribute the electrical current to the spark plugs in the correct order. In the 1980s, automakers began using distributor less ignition systems. These are sold-state electronic systems which require no moving parts, and they are therefore much more reliable than the older systems. No matter what kind of ignition system a vehicle has, a failed ignition switch will prevent the vehicle from starting. Unfortunately, there are many other reasons why a vehicle could fail to start, so failed ignition switches are not always easy to diagnose. Symptoms can include an engine that will not crank when the key is turned or a starter than keeps running after the key is released. These symptoms can also be caused by other problems such as weak battery or corroded connections, so it may be necessary to obtain a mechanic’s diagnosis. If jiggling the key in the ignition fixes the problem, then the ignition switch is probably the culprit.