Trouble Code Read

Step 10 - The reader will present an option to recheck the system and give a "PASS" reading if the system detects no problems.

Pass Indicator

Step 11 - After the reader has finished, turn the ignition key to the "OFF" position.

Turn Ignition Key Off

Step 12 - Next, remove the data connector from the ALDL port.

Remove Data Connector

Helpful Information

Once the "check engine" or a "service engine soon" light has illuminated the computer has detected a problemĀ and stored one or more trouble codes. When this light is illuminated the vehicle enters into "limp mode", which means the system is not running at optimal performance. Most 1996 and newer vehicles utilize an ALDL connector port which is used to connect a reader for code retrieval. This connector is generally located on the drivers side near the footwell.

A trouble code definition chart can be used to help define the meaning of the malfunction. After repairs have been performed and codes cleared, the computer will start testing systems once the vehicle is driven. These monitors operate during normal driving conditions and can take up to 30 miles to complete. If the computer senses a problem, the check engine or service engine light will re-illuminate.

Vehicles older than 1996 use an OBD1 scanner or the use of an board retrieval method is required to gather trouble codes.

Common Problems

  • If a scan has been performed and a P1000 is observed it means the computer could not complete the retrieval process.
  • If the check engine or service engine soon light does not illuminate while the key is in the "ON" position repairs are needed such as an indicator bulb replacement.


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-01-06)