Noid Light – Learn how to test fuel injectors, using a noid light.

Noid Light - Learn how to test fuel injectors, using a noid light.
Noid Light - Learn how to test fuel injectors, using a noid light.

Learning how to test fuel injectors, using a noid light, is easier than you think.

So, a fuel injector noid light kit, should be on your must have tool list.

Also, noid lights come in a variety of different types, and are relatively inexpensive.

Get a good noid light kit, one that comes with all the attachments you need for any vehicle.

So, noid light kits, contain lights for the different fuel injector connectors, used on the majority of makes and models.

Because, not all cars, use the same fuel injector connector type. A fuel injector noid light, will help you to troubleshoot a misfire, no start and other fuel related issues.

Noid Light Test Kit
Noid Light Test Kit

It is one of those MUST HAVE tools, to diagnose the majority of, fuel injected engine problems. This test will tell you if the computer is pulsing the fuel injectors open, when cranking the engine over. You will be able to see if, a certain fuel injector is getting a signal to fire.

So, all fuel injectors need power and a switching signal, from the fuel injection computer. This tool helps you to, visually confirm that the fuel injector is getting both. A fuel injector noid light test, will not tell you that the fuel injector is bad. But, it will confirm that it is getting power and the switching signal.

Noid Light Testing

Fuel System Testing
Fuel System Testing
  1. Locate the fuel injector that you are going to test and disconnect it from its electrical connector.
  2. The fuel injector may have a metal clip, securing the connector to the fuel injector. So, you will need to press it in, to unlock the connector and remove it.
  3. The connector will have a plastic locking tab integrated into it; that needs to be pressed, as you gently pull back on the connector.
  4. Once the fuel injector connector is removed, insert the fuel injector noid light into the connector.
  5. It should fit into the connector, as easily as the fuel injector did.
  6. Do not force the noid light into the fuel injector connector.
  7. When ready and a safe distance from the engine, have a helper crank the engine over.
  8. If all is well, the light will flash on and off, the whole time the engine is cranking.
  9. If the engine started, the light should flash on and off, the whole time the engine is running.
  10. Now, if the light did flash on and off, it’s always a good idea to test the fuel injector connector; next to the one you just tested and compare both results.
  11. Finally, if all is good, both connectors should make the light flash, in the exact same way.

Interpreting The Results, Of The Test

Noid Light Test Results
Noid Light Test Results
  • So, did the light flash on and off? And, was this flashing, comparable to the fuel injector connector next to it. If it was, this result indicates that the fuel injector, is getting power. Also, that the fuel injection computer, is providing a fuel injector pulse signal to activate it.

Consequently, the test results, eliminate the electrical end of the fuel injector circuit; as the cause of the problem or misfire.

  • If the light DID NOT flash on and off, this result indicates that the fuel injector; is either NOT getting power or that the fuel injection computer; is NOT providing a fuel injector pulse signal to activate it. With this result; you have confirmed that, the electrical part of the fuel injector circuit is at fault.

Noid lights, What Are They Telling You

Test Results
Test Results
  • If the noid light stays on, with the key on or when cranking; chances are wiring on the ground side of the circuit is either shorted out (shorted to ground); or the driver inside the computer is bad and the computer may need to be replaced.
  • And, if the noid light does not flash at all, when cranking the engine over; check for fuel injector pulse at multiple cylinders, as you may just have an issue with that specific circuit.
  • If there is no pulse on all cylinders; check to see if the fuel injector is getting power with the key on and cranking. If still no injector pulse; then the computer is not pulsing the injectors open for some reason and more testing will be needed.
  • Again, you want the noid light to, blink constantly when cranking the engine over. This is a good sign. So, there you have it. Problem Solved !! or Now you know where to look next.

Keep in mind that when you are testing with a noid light; this test will not tell you if your injector has gone bad. But, it will tell you if your (ECU) or (PCM) is sending the signals; needed for your injector to work correctly.


So, fuel injectors are vital in the functioning of your car. Also, the most common reason why, cars fail to start is, because of problems with the fuel injection system. Finally, using a noid light, can help you diagnose some of the issues common with fuel injector problems.

Thank You !