How To Test A BAD Fuel Injector (2008-2010 2.4L Ecotec)

You'd be surprised just how easy it is to diagnose a bad fuel injector on your 2008-2010 2.4L Ecotec equipped vehicle. For the most part all it takes is a simple multimeter resistance test.

In this tutorial I'll show you how to do it in a step-by-step way. Also, if you don't know where to start your troubleshooting efforts, on the next page I'll explain to you my method of finding the bad or clogged fuel injector.

Contents of this article at a quick glance:

  1. Symptoms of Bad Fuel Injector.
  2. Checking The Injector's Internal Resistance.
  3. How To Find The Bad Or Clogged Fuel Injector.
  4. Where To Buy The Fuel Injector and Save.

Symptoms Of A Bad Fuel Injector

For the most part, a fuel injector will fail in one of two ways. It will either become clogged or suffer an internal short. Both of these will cause a rough idle/misfire condition.

Now when the fuel injector becomes clogged, it's unable to spray (atomize) fuel correctly into its cylinder. When the injector suffers an internal short (to its coil winding), it stops injecting fuel completely.

Since a fuel injector injects the gasoline the cylinder needs to produce power, when one fails (or gets clogged) it'll have serious repercussions in engine performance. Here are the most common symptoms you'll see when a one fails:

  1. Rough idle.
  2. Lack of power.
  3. Hesitation when you accelerate your 2008-2010 2.4L Ecotec down the road.
  4. Fuel injector trouble codes: P0201, P0202, P0203, P0204.
  5. Misfire trouble codes:
    1. P0300: Random Cylinder Misfire.
    2. P0301: Cylinder #1 Misfire.
    3. P0302: Cylinder #2 Misfire.
    4. P0303: Cylinder #3 Misfire.
    5. P0304: Cylinder #4 Misfire.

The test I'm gonna' show you deals primarily with shorted fuel injector coil windings. But, I'll also offer you a specific diagnostic strategy to find a clogged fuel injector (in the next page, heading: How To Find The Bad Or Clogged Fuel Injector)

Checking The Injector's Internal Resistance

Checking The Injector's Internal Resistance With A Multimeter. How To Test A BAD Fuel Injector (2008-2010 2.4L Ecotec)

To test the resistance of the fuel injectors, and see if it's shorted or not, you'll need a multimeter. If you don't have one check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.

The factory fuel injector resistance for the 2008-2010 2.4L Ecotec is 11 to 14 Ohms ().

Even if you suspect that only one fuel injector has failed, I'm gonna' suggest that you test the resistance of all four (especially since they're all very accessible).

NOTE: Your fuel injector resistance test should be done with your 2008-2010 2.4L Ecotec's engine cold. If the engine has been running for any extended length of time, let it cool down completely.

These are the test steps:

  1. 1

    Disconnect the fuel injectors from their engine wiring harness connectors.

    NOTE: To identify which cylinder the fuel injector belongs to, see the above illustration with the cylinder # id for the 2008-2010 2.4L Ecotec.

  2. 2

    Set your multimeter to Ohms (Ω) mode and:

    Measure the resistance of the fuel injector across its two male spade terminals with the multimeter test leads (see the illustration in the image viewer).

  3. 3

    Write down the resistance value that your multimeter records for the specific fuel injector you're testing. The illustration above will help you identify the cylinder # the fuel injector belongs to.

  4. 4

    Repeat steps 1 through 3 on the remaining fuel injectors.

    NOTE: The fuel injector resistance specification is: 11 to 14 Ohms.

Let's find out what your specific multimeter test results mean:


CASE 1: Your multimeter confirms that all four fuel injectors' resistances are within specification. This is good news since it confirms that your 2.4L Ecotec engine's fuel injectors are not shorted or open internally.

If you suspect that you have a clogged fuel injector, which a resistance test won't find, take a look at the following section: How To Find The Bad Or Clogged Fuel Injector.

CASE 2: One of the fuel injectors registered a resistance value not within the specification. This indicates that the fuel injector is BAD. Replace the fuel injector.