How to Check Engine Codes for Vehicles

by Contributing Writer; Updated June 12, 2017

OBD II universalized the equipment and adapters needed to diagnose check engine codes on all passenger Vehicles and light-duty Vehicles. 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 Vehicles specific makes and models. While OBD II scanners were expensive and cumbersome to use Vehicles first, there are now affordable pocket scanners Vehicles the home-mechanics to diagnose their own Vehicles.

Under The Hood:

 How to Check Engine Codes for a Dodge Ram

1994 Through 1997 Models

Insert the key in the ignition and turn the ignition on and off quickly in this sequence: on, off, on, off, on. Don't crank the truck. If you crank the engine by mistake, begin the sequence again as the process will be aborted.

Observe the "check engine" light. It will begin to make a series of flashes, indicating two-digit codes that represent the problem with your truck. The light will flash several times for the first digit, pause, then flash several more times to indicate the second digit.

The "check engine" light will flash Code 55 to signal the end of all codes. If your engine has stored no codes, the light will only flash Code 55.

1998 and Newer Models

Turn the ignition on while pushing the odometer clearing button simultaneously. Engine codes will read on models with digital odometers. This feature also tests all dash panels.

Turn the key to the "on" position. In some models, this alone will activate the trouble code sequence.

Invest in a diagnostic code scanner or take your Ram to a local auto parts dealer for testing. Basic scan tools begin around $50 and can go up to as much as $5000 for professional devices.

 How to Check Engine Codes for a Chevy Avalanche

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.

Items you will need

  • OBD II pocket scanner with operation manual

  • OBD II diagnostic codes

 How to Check Engine Codes for the Mazda B2200

Warm up the engine for one to two minutes before shutting it off. This will cause any problems with the Mazda to show up during the diagnostic reading.

Pop open the hood and locate the "Tester" box, which is a 2-by-2-inch box on the driver side of the engine.

Find the connections labeled "STI and "SIG RTN." Securely connect a 3-inch metal wire, with a plastic protective covering, from the SIG RTN to the STI slot. Wiggle the wire to ensure the wire will not become loose during the test.

Turn the ignition on, but do not start the engine. Watch for the blinking "Check Engine" light. With a paper and writing utensil, write down the pattern of short and long intervals between flashes of light. The intervals corresponds with codes in a repair manual. Check your local library, repair shop or online database for a list of engine codes.

Items you will need

  • Paper

  • Writing utensil

  • 3-inch wire (stripped)