What is an OBD (On-Board Diagnostics) Scanner?

May 26, 2022

A man is working on the engine of a car in a garage.

On-Board Diagnostics (OBD) scanners are used to discover potential problems with your car. It connects to the car's internal computer system.

OBD scanners are plugged directly into the OBD port in your car which scans the stored data to identify everything from loose wires to oxygen level issues. OBD scanners use error codes to display the automotive issue.

The scanner reads the data which is recorded using Electronic Control Units (ECU) which are tiny computers also known as subsystems, each controlling a different vehicle part.

When you start your car, the OBD system starts scanning the engine components to check performance. If there is a major error the "check engine" light will switch on. While it is not time to panic, it is a good idea to have your vehicle checked if this happens.

The OBD system tracks and detects errors, for any component that impacts the engine. Some important components would be:

Every vehicle error is diagnosed and is given a code which is stored in the OBD system. When the scanner is plugged in it reads the codes and finds out what is wrong with your car!

The OBD scanner reads these diagnostic trouble codes stored in the system. Each code is unique so it takes some code reading to get the answers. The codes typically start with a letter which indicates the buggy system and is followed by five digits to give the specific issue. There are codes for the body, power train, chassis, and network:

Not only do OBD scanners keep tabs on your vehicle's health, they can also help save time, money and frustration! If you need computer diagnostics performed, give our auto repair shop a call today!

Simple Habits That Will Double the Life of Your Car's Engine - Toole's Garage
November 4, 2025
In this article, we’ll share a few simple yet powerful habits that can add years to your vehicle’s life and save you money in the long run.
How to Spot a Failing Water Pump Before It Overheats Your Engine | Toole's Garage
October 31, 2025
Toole's Garage in California highlights the warning signs of a failing water pump before it leads to engine overheating.
October 30, 2025
Seeing that little engine-shaped icon glow on your dashboard can be unsettling. We get it—your car seems fine, maybe even drives “just the same,” but the warning light won’t quit. Here in Stockton, where our vehicles face dust, variable traffic, and stop-and-go commutes, we’ve seen plenty of drivers shrug off the illuminated warning. In this article we’ll demystify the “Check Engine” light (CEL) , explain some of the most common causes, why ignoring it can cost you more than you expect, and why scheduling a diagnostic sooner is the smart move.
More Posts