Diagnosing Intermittent Car Problems


When a vehicle has a problem that occurs unpredictably it is called an intermittent problem. An intermittent problem may not occur while operating the system or even during a test drive. This can make it very difficult to diagnose the cause of the problem.

Intermittent car problems can be a pain for everyone involved!

This post should help you understand why that is and the complexities of diagnosing the cause of car problems. And in doing so, hopefully relieve any related frustration. Fortunately, Community Auto is equipped with the latest repair information, technical service bulletins, and recall information. If your vehicle has a system or component with an inherent safety, emissions, or reliability problem and there is a factory fix available for it, we will be able to make you aware of it and repair the problem for you. What you can do to save money, time, and frustration and to help us solve the problem:

Pay attention to driving conditions

  • What is the temperature like outside?
  • Is it the first time the vehicle has been driven for the day?
  • Have you been in stop and go traffic or turning and off your vehicle frequently (such as while running errands)?
  • How long and at what speeds were you driving when the problem occurred?
  • Was the A/C, heat, lights, or radio on?

These can all be clues that help us get closer to solving the problem and ultimately save you time and money in the process.

Regardless of the type of problem or the system at fault, certain aspects of diagnosis remain the same. In order to accurately diagnose the cause of any problem the technician needs the problem to (predictably) occur twice. The first observation provides the technician with some insight needed to plan a focused testing strategy. A focused testing strategy saves diagnostic time and dollars. The second observation is made while the technician has his test equipment hooked up, monitoring the system or components that may be involved. Although the technician is prepared to attempt to recreate whatever operating conditions are necessary to make the problem occur, if the problem does not surface, a focused strategy cannot be planned.

In this case the technician must test all systems that could potentially cause the symptom until a defect is found. This all-inclusive systematic method takes more time and dollars, and there is no guarantee that the correction of a defect discovered this way will resolve the problem.

This is because there is no proof of a defect discovered during this systematic testing is the real cause of the problem. Another strategy to fix an intermittent problem is to perform a repair based on an educated guess of what is causing the problem. This can be risky because, in most cases, the part cannot be returned and the labor for the installation is non-refundable. However, when the symptom cannot be observed or testing does not disclose the defect, it can be the only choice left.

Diagnosing intermittent problems can be very time consuming and requires your patience and cooperation for us to be successful fixing the problem. It may require more diagnostic time than originally estimated to recreate or find the cause of the symptom. It may be necessary to leave the vehicle for several days, or return several times, so we may observe the symptom or judge the results of diagnosis and/or repair to insure the problem is corrected.

The service advisor will give you an initial estimate for diagnosis. This estimate is an educated guess of how long it may take to discover the cause of your problem. This initial estimate does not guarantee a discovery of the cause of the symptom or include the cost of repair. The repair cannot be estimated until after the diagnosis is completed. During the course of the diagnosis we will keep you informed of our progress. If additional diagnostic time is required to discover the cause of the problem, we will ask for your authorization of the cost before proceeding. After diagnosis we will ask for your authorization of the repair cost before proceeding.

Now that you are aware of some things that can come up when trying to fix an intermittent problem, it is time to talk to the service advisor about the specifics of your situation.

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