How To Test The Fuel Injectors (2002-2005 GM 2.2L Ecotec)

A failed fuel injector will cause your 2002-2005 2.2L Ecotec equipped GM car (Cavalier, Classic, Alero, Grand Am, and Sunfire) to misfire.

Troubleshooting a failed fuel injector is not that hard and in this tutorial I'll show you how.

You can find this tutorial in Spanish here: Cómo Probar Los Inyectores De Combustible (2002-2005 2.2L Ecotec) (at: autotecnico-online.com).

Symptoms Of A Bad Fuel Injector

The fuel injectors are the ones responsible for getting the fuel into the engine cylinders. If any one of them gets clogged or stops working, your 2.2L Ecotec engine's performance is gonna' suffer.

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 car down the road.
4. A fuel injector trouble code:
   • P0201: Cylinder #1 Fuel Injector Control Circuit.
   • P0202: Cylinder #2 Fuel Injector Control Circuit.
   • P0203: Cylinder #3 Fuel Injector Control Circuit.
   • P0204: Cylinder #4 Fuel Injector Control Circuit.
5. Misfire trouble codes:
   • P0300: Random Cylinder Misfire.
   • P0301: Cylinder #1 Misfire.
   • P0302: Cylinder #2 Misfire.
   • P0303: Cylinder #3 Misfire.
   • P0304: Cylinder #4 Misfire.

Fuel injectors usually fail in one of two ways. They either become clogged and don't inject enough fuel, or their internal coil winding shorts out and stops injecting fuel completely.

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

Testing the fuel injector involves checking its internal resistance. To be a bit more specific, we're gonna' check its coil winding resistance to see if it's suffered an open or short. It sounds complicated but it's not!

OK, the factory fuel injector resistance for the 2002-2005 2.2L Ecotec Cavalier, Classic, Alero, Grand Am, and Sunfire is 11 to 14 Ohms (Ω). So all four fuel injectors should be within this range.

NOTE: Your fuel injector resistance test should be done with your GM vehicle'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 2.2L Ecotec equipped GM vehicle.

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 above).

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: All fuel injector resistances are within specification. This is the expected and correct test result and tells you that none are 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.