Check Engine codes are the best way to diagnose problems with modern cars. Every time the Check Engine light comes on, the code that triggers it is entered into the engine control unit. An on-board diagnostics scanner is used to pull these codes from the ECU. The code can then be cross-referenced against the list of Check Engine codes to determine the problem that triggered the light.
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Things you need
- On-board diagnostics scanner
Place the keys in the ignition switch and turn it to Off.
Connect the on-board diagnostics scanner to the Engine Control Unit data link in the lower part of the instrument panel. It is located beneath the steering column.
Turn the ignition switch to On and turn on the scanner. Follow the on-screen instructions. The scanner will report the Check Engine code as an alphanumeric code beginning with the letter "P" and followed by four digits.
Compare the code against the List of Diagnostic Trouble Codes found in the service manual for your car's make and model. If a service manual is not available, an online search with the exact code, make and model will often return a description of the problem.
Tips and warnings
- Many automotive repair stores will pull Check Engine codes for little to no cost.
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