FAQ – What is a Noid Light

FAQ – What is a Noid Light


An automotive noid light is to test the fuel injector operation in any EFI vehicle. Problems with your fuel injector can cause your engine to run rich or lean, or have misfire issues. This is when you will be using a noid light to ensure that your fuel injector is working correctly or not.

If your car does not start or the engine is not starting for some reason, a noid light is just one part of the testing procedure to see what is wrong. When you have tested for spark and fuel pressure in your engine but your car is still experiencing a NO START condition, you must use the noid light to test your fuel injectors.

In any EFI system your fuel injectors must receive a pulsing signal and power to operate correctly. This is sent from your Powertrain Control Module or PCM / ECU. When your car won’t start you’ll be using an injector noid light to confirm that your fuel injector is getting what it needs to work.

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Keep in mind that when you are testing with an automotive noid light, this test won’t tell you if your injector has gone bad. Rather this will tell you if your ECU or PCM is sending the signals needed for your injector to work correctly.

Most noid light kits will include several sets of lights to cover most makes and models. This helps you test your EFI system no matter what vehicle you happen to own. This is because each manufacturer has different fuel injector clips, and can vary depending on the year range (OBD1 vs OBD2)

what is a noid light

How To Use a Noid Light

To use a noid light you will need to open your hood and locate your fuel rail or rails. Your injectors will vary depending on the year range, and there’s more than likely a locking clip that must be depressed. In the example above the metal clip must be pressed down to unplug the fuel injector clip.

Some others types of OBDII fuel injector clip must have a metal pin removed in order for you to fully remove the connector. Once your EFI connector has been removed you can insert the fuel injector noid light into the harness.

Never force your noid light into the harness or into the fuel injector clip. This should easily slide into position and create a firm connection for you to test. Never use a noid light that’s intended for a different vehicle, and always exercise safety around your engine bay.

Now that you are ready to test your fuel injector harness, stay clear of your engine bay and have a friend crank over your engine. You should see the light illuminate and turn off while your friend is cranking over your engine. If there is no response from the light check the connection in your fuel harness and repeat the test.

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If the fuel injector harness does light up, this means that your injectors are receiving power from your ECU. This is the first step and the next step is to unplug the next injector and insert another light to see if the lighting pattern is similar.

This test should tell you whether or not your fuel injector harness is the problem behind your misfire. If your car does not start properly or starts slowly, this test can also help you identify whether or not the injectors should be firing properly.

You now know how to use a noid light and what it is. Have any questions about our guide? Leave us a comment below and let us know!