How Does Your Mechanic Diagnose Problems With Your Car?

24 July 2019
 Categories: , Blog


If your car is making a weird noise, producing a weird smell, or just isn't driving right, then you're probably about to drop it off at your local mechanic. If the problem is simple or obvious, then an experienced mechanic will probably be able to pinpoint it right away and get to fixing it. Not all car repairs are so simple, however, and many problems require significant amounts of diagnostic effort to actually fix. In some cases, diagnosing a problem may be much more difficult than actually fixing it.

Luckily, automotive technicians have a variety of tools and techniques available to help them to determine exactly why your car isn't behaving properly.

Onboard Diagnostics

If your car was made anytime in the last several decades, then it uses a system called Onboard Diagnostics II (OBDII). This system tracks data from various sensors in the car and reports on problems. When your car's check engine light turns on, it's because the OBDII system has detected a problem and stored a code in the computer. OBDII was originally focused primarily on emissions equipment, but it has evolved to become an all-in-one stop for sensor data.

Even if your check engine light isn't on, most technicians will begin their diagnostic process by plugging into this system. In addition to checking for codes that may not have yet triggered the light, they can also use this to read real-time data from a variety of vehicle sensors. If your technician suspects a particular problem based on the symptoms that you describe, then often sensor data can confirm or rule out that suspicion.

Manufacturer Specific Diagnostics

In addition to the OBDII system, many cars have manufacturer specific computer systems. Although reading data from an OBDII equipped car can be done easily and cheaply with a variety of tools, reading manufacturer specific data is often much trickier. Fortunately, shops that are properly equipped can glean significantly more information from these systems. If the onboard diagnostics are not providing enough data, then this will sometimes be the next step.

Smoke Tests and Other Specialized Diagnostic Tests

If your technician has narrowed the problem down, then they may move on to some highly specific tests. If your car is suspected of having a vacuum leak, for example, a diagnostic technique known as a smoke test is likely to be used. As the name implies, this involves pumping smoke into the engine to detect leaks in the vacuum system. For AC leaks, special UV dye is often added to refrigerant to find the source of the problem.

The Human Brain

Of course, collecting information about a problem is just the start. After pulling data from your car's computer and running any tests that may be necessary, your technician will draw on their own knowledge and experience. Often, the diagnostic systems in a car cannot tell a mechanic exactly what is wrong. Instead, data from the systems and from your car's many sensors provide clues that, when taken together, can allow a technician to zero in on the actual problem and get your car back on the road.

For more information, contact local professionals like those found at Nortown Auto LLC.