Intermittent electrical faults can drive a technician to distraction. The story typically goes like this: The vehicle comes in with a trouble code stored in the history, or the driver complains about an electrical component acting up “once in a while.” Then, when the technician tries to duplicate the problem, it doesn’t come back.
It is often very difficult to duplicate the exact conditions the driver experienced when the problem occurred. While there are a variety of reasons for intermittent electrical problems, few technicians may ever consider vibration as the culprit.
Everything has a point where it starts vibrating, depending on the frequency. So let’s use the rubber grommets on a control module that are a bit dried out and loose as an example. The module may move around a little anytime the vehicle is in operation, and nothing happens. However, when the frequencies reach the vibration point of the control module, it could start to dance around like a can in a paint shaker. Unfortunately, when that point arrives, it may not be possible to see it because the vehicle is moving.
Now, I can’t tell where every vibration may originate, and I don’t have some magic formula to solve it. However, an awareness that vibration can be a problem gives the tech one more thing to look for. Check wear on grommets or places where metal-on-metal contact occurs. Also, ask the driver if there are any new vibrations or sounds because they could be a helpful clue to find out when and where the problem occurs.