If one or more fuel injectors go bad on your GM 2.2L equipped vehicle, they will set the dreaded misfire codes: P0300, P0301, P0302, P303, P0304 and fuel injector codes (although this is not an absolute truth, since you could have one bad fuel injector and No codes).
This article will show you how to do an easy resistance test with a multimeter to test for a bad fuel injector. This article is a part of a series of misfire condition troubleshooting articles for your 2.2L GMC, Chevy or Pontiac equipped car or pick up. The starting point of this testing series is: How To Diagnose Misfire Codes (GM 2.2L).
Contents of this tutorial:
Tools You'll Need:
- Pen and Paper
The Fuel Injector Test
Your car's engine needs to be slightly warmed up for this test, but not completely cold. If the engine has been running for an extended amount of time, let it cool down about 1 hour. If you have a scan tool, you can verify that the engine coolant temperature (ECT) sensor reading should be no less and no more than 100° F.
To be able to accommodate all types of experience levels, and to keep this test as simple as possible, the following steps assume that you'll be testing all 4 fuel injectors.
Disconnect all four fuel injectors from their electrical connectors. Be careful, the connectors are made out of plastic and could easily break. Take your time disconnecting them.
Once all of the fuel injectors are disconnected, test each one with your multimeter in Ohms mode. You'll do this by probing the male spade terminals inside the fuel injector with the multimeter's test leads.
It doesn't matter what color test lead you use to test either of the two fuel injector male spade terminals, the polarity of the leads is not important when testing the resistance of the fuel injectors.
After verifying the resistance value, write it down on a piece of paper. Don' forget to write down what cylinder that reading belongs to.
The fuel injector resistance should be around 1.9 to 2.3 Ohms (although on your specific GM 2.2L car or pick up, this value might be a little different). Now, repeat test steps 1 through 4 on the remaining 3 fuel injectors.
Alright, with the resistance values in hand, of all four fuel injectors, let's interpret your results. Choose from one of the following CASES:
CASE 1: All of the multimeter resistance values are nearly identical. This result indicates that the fuel injectors are OK and are not causing the misfire code or condition.
If your 2.2L equipped GM vehicle is still suffering a rough idle/misfire problem, then there's a good chance that the problem is being caused by low compression in one engine cylinder or a bad spark plug wire/bad ignition coil. For more troubleshooting ideas, take a look at the following section: Fuel Injector Troubleshooting Guide and the following tutorial:
CASE 2: One of the four multimeter resistance values is drastically different: Retest all four fuel injectors to confirm the initial resistance values your multimeter registered. If they are the same as before, then the fuel injector that registered the different resistance value is bad. Replace the fuel injector.
If you're interested in saving some bucks on the original AC Delco/Delphi fuel injector, take a look at the section: Where To Buy The Fuel Injector And Save.
Which Fuel Injector Do I Test First? Or Do I Test All Of Them?
It's best to test all of the 4 fuel injectors on your GM 2.2L equipped car or pick up (Cavalier, S10, Sunfire, Sonoma). This way, you'll have a clear idea of what the resistance value should be for all 4 fuel injectors.
To explain this a bit further, let me say that you need to keep the following two important points in mind:
- All fuel injectors have a specific internal resistance that can be measured in Ohms mode on a multimeter.
- When a fuel injector goes bad, it'll normally have a completely different resistance value than the other ones.
Therefore, the purpose of the test is to find the bad fuel injector by reading it's resistance and comparing this reading to two other fuel injectors.
If you have a scan tool and you have specific misfire code, test the fuel injector that correspond to the diagnostic trouble code and then test two more, so that you'll have those two resistance readings to compare.
If you don't have a specific misfire code to go on, well that's OK too, just test all of the fuel injectors.