How to Reset OBD Codes

by Brooke Julia
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OBD codes (On-Board Diagnostics) let you know something is wrong with your car's engine. Once the problem has been repaired, the code should either erase itself or be removed. It's inadvisable to reset an OBD code without addressing the problem that caused it, as the light will simply reappear again over time and you may be risking serious damage to your engine. Several ways are available to erase codes at home, though not every method will work for your vehicle. The only sure way to remove codes is by using a scanner.

Step 1

Connect your vehicle's diagnostic terminal, usually called the Assembly Line Diagnostic Link (ALDL), to a code scanner and turn the ignition on. Use either an OBD1 or an OBD2 scanner, depending on the age and computer system of your vehicle. The scanner reads the codes stored in the computer and then gives you the option to clear them. Select that option.

Step 2

Go to a local auto parts store like Auto Zone, Advance Auto or Pep Boys to ask for a free OBD code reset if you don't have a scanner. Most chain auto parts stores offer this service, including reading the codes for you, free of charge.

Step 3

Disconnect your battery. Remove the negative battery cable first, then the positive and allow the car to sit for a few minutes. Reconnect, using the positive first and then the negative. This resets the engine codes in some vehicles, though it also interrupts other functions, such as the clock and the radio settings.

Step 4

Let the engine codes disappear on their own if you've fixed the source of the problem. Several successful engine ignitions and runs allows the "check engine" light to extinguish. If your car continues to run well for a specific amount of time after that–the time differs for each make and model of car–the code will reset within the computer.

Step 5

Force the automatic code clearing by cranking your engine, driving forward several yards, then reversing several yards. Shut the engine off and repeat three times. This imitates the successful runs and shuts off the "check engine" light on the dash by the fourth crank.

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