How to Check Engine Codes for a Chevy Avalanche


Manufactured in 2002, the Chevy Avalanche has always integrated a second version of on-board diagnostics (OBD II). OBD II universalized the equipment and adapters needed to diagnose check engine codes on all passenger vehicles and light-duty trucks. Prior to the implementation of OBD II, computers in cars that would trigger check engine lights (also known as malfunction indicator light or MIL) to appear (indicating an engine code) and often used custom equipment for specific makes and models. While OBD II scanners were expensive and cumbersome to use at first, there are now affordable pocket scanners for the home-mechanics to diagnose their own vehicles.

Things You'll Need

  • OBD II pocket scanner with operation manual
  • OBD II diagnostic codes
  • Open the driver's side door of the Chevy Avalanche. Bend over under the driver's side dash and locate the diagnostic link connector (DLC). It is on the left hand side of the steering wheel under the dash. This 16-prong trapezoidal-shaped connector matches the shape of the plug at the end of the cord on the pocket scanner.

  • Plug the pocket scanner into the DLC. Because of its shape, you can only plug it in one way. The battery of the Avalanche will provide power to the pocket scanner so an "On" button is not required.

  • Place the ignition switch in the accessory power position. This is also known as the key-on/engine-off position. The battery will provide power to all the accessories without the engine running.

  • Refer to the operation manual of the pocket scanner. There are many brands with variable options and most of them function similarly. Operating most pocket type scanners is basically self-explanatory.

  • Follow the onscreen menu on the pocket scanner and use the available scroll button(s) to choose the "DTCs" (diagnostic trouble codes) or the "Read Codes" option and then press the "Enter" or "Send" button. It will take a moment for the scanner to read any codes or pending codes.

  • Jot down the engine code numbers on the Avalanche with a pen on a piece of paper. Most pocket scanners may offer a brief code description or may simply show the number of the code. P-codes (powertrain) are the most common, but you may see C-codes (chassis), U-codes (invalid or missing data) or B-codes (body).

  • Refer the number to the operations manual for the pocket scanner. Most common codes are listed in numeric sequence and will give you a general description of the engine code. Understand this description may not pinpoint the problem with the Avalanche and more professional diagnostics may be required. For most P-codes (the most common), you can usually figure it out or talk to an auto parts store person for help diagnosing the engine code.

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