How to build a mil eliminator

Written by katrina matterhorn
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Malfunction Indicator Light (MIL) eliminators are designed to shut off the "Check Engine" light and improve the performance of your car if you have modified it for racetrack use. Removing a car's catalytic converter or replacing your midpipe for racetrack or off-road use causes your "Check Engine" light to remain blinking. The MIL eliminator is designed to connect to your car's O2 sensors, thereby blocking off the codes they generate which cause the "Check Engine" light to blink. Building your own MIL eliminator in order to increase your car's performance requires a few steps to set up.

Skill level:
Moderately Easy

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Things you need

  • 1 PC board
  • 2 tantalum capacitors
  • 1 package of 5 mega OHM resistors
  • 25 feet of 20-gauge wire
  • Solder
  • Electrical tape
  • Soldering iron

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  1. 1

    Locate your O2 sensors at the rear of your car and remove them. Carefully cut off the outer sheathing of the O2 sensor wires. You will notice a grey wire, a black wire and two white wires. Mark one of the white wires to be matched up to their original configuration once you have built your MIL eliminator.

  2. 2

    Cut through all four wires halfway between the connector and O2 sensors. Cut the wire covering so that 1/2 inch of each wire is exposed. Cut four equal strips of the 20-gauge wire and strip them so that 1/2 inch of each wire is also exposed. Decide on the measurement of each strip dependent upon the size of your midpipe.

  3. 3

    Solder the wires to the two halves of the O2 sensor wiring harness and match the colours together. Use the electrical tape to tape each solder point. Add an extra layer of tape.

  4. 4

    Cut the black and grey wire in the middle of the harness. Strip the wires so that 1/2 inch of the wire is exposed. Solder all the wires to the copper circle side of your PC board.

  5. 5

    Wrap the area of the harness entirely with your electrical tape. One end of your PC board should have the connector, and the other end should have the O2 sensor wires. Unplug your battery terminals and reconnect your O2 sensors to your car. Plug the connector ends back into your car. Wait five minutes and reconnect your battery terminals.

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