How to Check Emission Trouble Codes With an Ignition Switch


Some older vehicles are not equipped with an access port to connect a scan tool to check the status of your vehicle's systems. If your "check engine" light has come on and you don't have a way to directly connect to the on-board diagnostic system, you'll need to use the "ignition key dance" method. This method consists of turning the ignition key to access the diagnostic computer. The check engine light will then flash, telling you the codes you need to fix your vehicle.

  • Insert the ignition key into the ignition cylinder and lock mechanism.

  • Turn the key to the "On" position and then to the "Off" position. The sequence that is most common is "On-Off-On-Off-On." You must do this within five seconds on GM vehicles, and within five to seven seconds on most other vehicles.

  • Examine the "check engine" light. It should start blinking. These will be the engine codes. Normally, there will be two sets of blinking lights. The engine light will blink, then pause, then blink again. For example, if the check engine light blinks twice, then pauses, then blinks three times, this indicates code "23." Reference your vehicle's service manual to translate the numeric code.

Related Searches


  • "Auto Repair For Dummies;" Deanna Sclar; 1999
  • "How To Repair Your Car: Car-Care Tips, Simple Repairs, Driving & Maintenance Tips, and more;" Paul Brand; 2006
  • Photo Credit Jupiterimages/Polka Dot/Getty Images
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