How to Reset Codes on a 1998 Chevy S10 Blazer

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The plug for an OBD II scanner connects to the data link connector.

As is the case in all vehicles equipped with on-board diagnostics, trouble codes will set off the "Check Engine" light on the 1998 Chevy Blazer, though on the Blazer it's called the "Service Engine Soon" light. It is universally referred to in the automotive-repair industry as the "Malfunction Indicator Light." Hundreds of faults can trigger the light. Before resetting the light, diagnose the code and make any necessary repairs. Simply resetting the codes will only mask the existing problem and damage to other components may occur.

Step 1

Open the driver's-side door of the Blazer and locate the data/diagnostic link connector (DLC) under the driver's-side dashboard. It is tucked up underneath the dash near the parking brake pedal to the left of the steering column.

Step 2

Connect the plug of the scanner to the DLC.

Step 3

Turn the ignition key to the "ACC" power position to illuminate all the instrument cluster lights, but without the engine running.

Step 4

Press the "Erase" button on the scanner, if it is equipped with one. If not, some scanners may require scrolling through the onscreen menu display with an up or down (or both) scroll button(s). Scroll to the erase codes option (it may say "erase DTCs" for "diagnostic trouble codes") and press the "Enter" button. Toggle to the "Yes" option with the scroll button, if applicable, and press the "Enter" button again. Wait until the scanner defaults to the main menu or the onscreen display confirms "Command Sent."

Step 5

Start the engine and look for the "Service Engine Soon" light on the instrument cluster. If the light is still there, repeat the process. If the light remains there after the second attempt, the Blazer most likely has a "hard" trouble code that needs to be diagnosed and serviced as soon as possible.


Resetting the engine codes in any OBD II vehicle is practically a moot point. If proper repairs have been made, the computer is going to relearn on its own, self-diagnose that the problem has been fixed and reset itself. However, after repairs have been made, resetting the codes can help expedite and monitor the computer during its relearning phase. Many scanners come equipped with inspection and maintenance monitor (I/M monitors) functions where the mechanic/owner of the vehicle can drive with the scanner plugged into the DLC and watch the progress of the monitors as they relearn and reset.

Disconnecting the negative battery terminal will also reset most trouble codes. Again, it will only mask an existing problem if repairs have not been made. If a scanner is not readily available, most auto-parts stores and many service stations will read codes for customers at no charge. Some may not be able to reset codes due to standards of service in the industry unless they know that repairs have been made.

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