Shop Talk Logo

What To Know About a Car Diagnostic Test

car diagnostic testingMost vehicle owners are pretty in tune with their cars. They become used to how the car drives, brakes, and even sounds. These drivers can also tell when something just isn’t right. Has it ever happened to you? You’re driving along and suddenly the car sputters or jerks forward and you think to yourself, “well, that’s never happened before.” Then, your head is filled with a flood of worry and questions. The best way to ease those concerns is by getting your car to a trusted automotive center for a diagnostic test. You may have many questions, but we have plenty of answers so that you can understand everything there is to know about a car diagnostic test.

Q: What is a car diagnostic test?

A: A diagnostic test determines the cause of a vehicle’s issue or cause of what has triggered the check engine light to come on. 

Q: How does a diagnostic test work?

A: Thanks to advances in technology in the automotive industry, vehicles have been manufactured with an internal computer that records, monitors, and operates many components within the vehicle. When something isn’t operating properly, a technician will utilize an advanced computer-type tool to connect to the vehicle’s internal computer (ECM or PCM) to read any codes stored and download information to help determine what area of the car needs attention.

Q: What systems are monitored by the car’s computer?

A: The engine, transmission, exhaust systems, brakes, and cooling system are all monitored by the computer. Though vehicle diagnostic scan tools have been instrumental in isolating vehicle troubles, they are unable to determine the exact cause of a breakdown or the check engine light’s illumination. While the code indicates to the technician which area of the vehicle needs attention or which component has fallen out of the acceptable range for operation, it does not provide details on what is responsible for the failure. That’s when the knowledge and expertise of a technician come in to properly diagnose and repair the problem.

Q: What can a car diagnostic tell you?

A: Using an OBD II (On-Board Diagnostics) interface, the diagnostic can provide information on ignition timing, level of buildup in the combustion chamber in the engine, the performance of fuel injectors, engine RPMs, and if the ignition coils are firing properly. The car records and stores the codes that pertain to different areas of the car. OBD II codes range from P0100 to P1899 with each letter and number translating to a certain function or malfunction. 

Q: Should I buy my own code reader?

A: DIY code readers are available; however, they are basic devices that do not provide much information as to the source of the problem. A scan tool like the kind your automotive shop utilizes is very expensive and takes training by a knowledgeable technician to operate and comprehend. Additionally, many vehicles have manufacturer exclusive trouble codes that make deciphering the code nearly impossible without an advanced reader.

Q: What is the benefit of having a diagnostic test?

A: In the past vehicle owners often sought help from a technician after a breakdown or major malfunction. Identifying problems in those cases were often time-consuming and very expensive. With today’s modern computerized systems, your vehicle is able to help determine when something is wrong often before a major breakdown occurs. In addition to codes helping identify areas of the car that require further scrutiny, the car’s computer may also store notifications from the vehicle manufacturer as well as some of the car’s performance history. 

Q: How long does a vehicle diagnostic take?

A: The amount of time to diagnose the vehicle’s issue is contingent on a few factors. A standard diagnostic test can take about an hour to an hour and a half. Of course, more complicated issues that require further diagnosis and where components must be removed for access or testing can take 2-3 hours; depending on the severity of the issue or multiple underlying issues.

Q: How much does a car diagnostic test cost?

A: Diagnostic tests are typically charged by the hour at the shop’s standard labor rate. Depending on the shop, the labor rate can range between $110 – $200 per hour. 

Q: How do I know if I need a diagnostic test?

A: If your check engine light comes on unless the scan indicates an error with the gas cap, a simple scan of the codes isn’t likely to provide much information as to what the problem may be. In that case, a diagnostic test is necessary. Also, if you notice something while driving that just doesn’t feel right, a technician may recommend a diagnostic to ensure major components are functioning correctly. 

Has your check engine light come on? Sun Devil Auto offers a scan of your on-board computer for diagnostic codes absolutely free! If further diagnostics are required, you can be assured that our ASE Certified expert Technicians can determine the cause of your vehicle’s issue and complete repairs in a timely manner. There’s no need to worry if your vehicle’s check engine light has come on, just bring your vehicle to a Sun Devil Auto near you for a diagnostic service you can trust!