How To Do A Noid Light Test (GM 2.2L)

Verifying that the fuel injector is indeed receiving Power and it's On/Off signal from the PCM (Powertrain Control Module) is a pretty simple and fast test on your GM 2.2L equipped vehicle (Chevy: Cavalier, S10 Pick Up, Pontiac Sunfire, GMC Sonoma). You'll need to use a Noid light for this test.

This article supplements the information in the article: How To Diagnose Misfire Codes GM 2.2L 4 Cylinder (P0300-P0304). Also, the info presented here applies to the GM 2.2L 4 cylinder equipped Chevrolet Cavalier, or Pontiac Sunfire, or Chevrolet Sonoma, or GMC Sonoma.

Here are the contents of this article at a quick glance:

  1. The Fuel Injector Noid Light Test.
  2. Interpreting The Results Of The Fuel Injector Noid Light Test.
  3. What Am I Testing With The Noid Light?
  4. Which Set Of Noid Lights Should I Buy?
  5. Related Test Articles.

Tools You'll Need:

  1. Fuel Injector Noid light.
  2. Multimeter
  3. A Helper

The Fuel Injector Noid Light Test

How To Do A Noid Light Test (GM 2.2L)

A Noid light is simply a little 12 Volt light bulb that has two terminals that fit into the fuel injector's connector.

The idea behind the noid light test is to see if the fuel injector is getting power and the activation signal from the fuel injection computer.

If both are present, the noid light will flash on and off, while you crank the engine.

If the noid light doesn't flash on and off (while cranking the engine), then that fuel injector connector is either not getting power or the activation signal (that comes from computer is missing).

This is what you'll need to do:

  1. 1

    Locate the fuel injector that you're gonna' test and disconnect it from its electrical connector.

    If you have already have a specific misfire code, like: P0301, P0302, P0303, or P0304, you can test that specific fuel injector connector for that specific cylinder that the diagnostic trouble code identifies... or you can test them all (which is my recommendation).

  2. 2

    Insert the Noid light into the connector, once you have unplugged the fuel injector connector from the fuel injector.

    Now, usually Noid lights are sold in a case that will contain several Noid lights for a variety of fuel injector connectors, therefore it's crucial that you use the right one. Using the wrong one will damage the female terminals inside the fuel injector connector. This will create a headache that you don't want to deal with... so be careful.

  1. 3

    Have your assitant crank the engine, once everything is set up, stand a safe distance from the engine, but within eye-view of the Noid light.

    NOTE: The engine may start or just crank and not start, depending on the issue that you're trying to troubleshoot/diagnose.

  2. 4

    You'll get one of three results:

    1. The Noid light will flash On and Off the whole time the engine was cranking or running.
    2. The Noid light did not flash On and Off at all when the engine was cranked or was running.
    3. The Noid light came On and stayed brightly lit the whole time the engine was cranking or running.
  3. 5

    Repeat the above 4 test steps on the other 3 fuel injector connectors. This is a key step, since you'll be able to compare a BAD Noid light test result with a GOOD test result in this manner.

Interpreting The Results Of The Fuel Injector Noid Light Test

OK, in this section, we're gonna' explore in depth the three Noid light test results. Choose one of the following CASES:

CASE 1: The Noid light flashed On and Off: This result indicates that the fuel injector is receiving Power and the On/Off signal from the Fuel Injection Computer. This flashing On and Off has to be compared to the results of the other fuel injector Noid light tests AND if the same, you now know beyond a shadow of a doubt that the circuits are OK.

CASE 2: The Noid light DID NOT flash On and Off: If this result is obtained from just one fuel injector connector, then it indicates that either power or the On/Off Signal, from the PCM, is missing.


If all of the fuel injector connectors did not flash On and Off, when the engine was cranked, this usually indicates one of several things: a) blown fuel injector fuse, or b) a bad Crankshaft Position Sensor, or c) an ‘open’ short in the wiring, or d) a BAD PCM, although this is rare.

CASE 3: The Noid light was lit brightly but did not flash On and Off: This result is usually a dead giveaway that the PCM is fried. In some rare cases... the circuit that feeds the fuel injector connector with the On/Off signal from the PCM is shorted to ground.

So, before you runoff and buy a new computer... get yourself a wiring diagram for your specific vehicle and check the continuity of the wires between the fuel injector connector and the fuel injection computer.