What is a Diagnostic or Trouble Code Test?

Knowing technical terms for automotive maintenance and repair is crucial for ensuring you are getting what you pay for. One thing that many customers hear is Diagnostic Testing. If you’ve heard the phrase “pull codes” referencing automotive repair but didn’t exactly grasp the concept, Casey’s in Chantilly, VA, is here to give you the details! 

What is a Diagnostic Test? 

A diagnostic test is performed when a warning light comes on in the dashboard. Think, check engine light. A diagnostic test on a car, truck, van, or SUV is used to check for issues. Components like the transmission, throttle, oil tank, and more offer codes to give insight into the vehicle’s health.

Onboard Diagnostics

The modern vehicles that we tend to see on the roads these days have internal computers. Those internal computers have on-board diagnostics, or ODB, that act as the vehicle’s diagnostic and reporting system which communicates trouble codes. 

What are Diagnostic Trouble Codes?

Diagnostic Trouble Codes (DTC) are pretty much how they sound. The vehicle’s onboard diagnostic system uses the codes to alert of a malfunction. 

The ODB system detects an issue and generates a code specific to the problem. 

How are trouble codes diagnosed?

The diagnostic system offers trouble codes that a technician can obtain by using a diagnostic scanner. They pull these codes by putting a vehicle through a diagnostic test. The technician will use a diagnostic scanner to “pull” the codes, and it tends to take only a few minutes. 

Check Engine Light Diagnostics at Casey’s in Chantilly, Virginia  

When a dashboard warning light blinks on, get your vehicle into Casey’s in Chantilly for a Diagnostic Test. When you bring your vehicle in for any service, we provide it with a courtesy inspection. Our courtesy inspection covers over 40 areas inside and out of the vehicle. We send the inspection report directly to your phone, including photos and descriptions of trouble areas. 


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