How to Test an HEI Module


The HEI, or high-energy ignition, module in your General Motors vehicle is one of the primary reasons for your vehicle starting properly. The HEI module sends the battery's initial spark to the various engine components, enabling them to start at the same time. If your vehicle fails to start, the issue may be with the HEI module. Thankfully, there is a simple test that you can perform to see if the issue is with the HEI module or something else. The only tool needed is a spark tester that can be purchased at most auto parts stores.

Things You'll Need

  • Spark tester
  • Turn the engine off. Open up the hood of your GM vehicle.

  • Disconnect the first wire from the HEI module. The first wire will be labeled with a large "1" on most GM vehicles. Use a socket wrench to remove the vehicle.

  • Insert a spark tester into the hole revealed by removing the wire.

  • Turn the engine on and have someone else inspect the HEI module. If a spark is emitted by the spark tester when the engine turns on, then the HEI module is functioning properly. If not, there is something wrong with your HEI module.

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