The simplest way to test the injectors is simply to listen to them with the engine running. Use either a stethoscope-type tool or the blade of a long screwdriver to touch each injector while the engine is idling. You should hear a distinct clicking as each injector opens and closes. Check that the operating sound increases as the engine speed is increased.
NOTE: The sounds of the other injector(s) may be heard, even though the one being checked is not operating. Listen to each injector to get a feel for normal sounds; the one with the abnormal sound is the problem.
Additionally, the resistance of the injector can be easily checked. Disconnect the negative battery cable and remove the electrical connector from the injector to be tested. Use an ohmmeter to check the resistance across the terminals of the injector. Correct resistance at 68°F (20°C) is 13–16 ohms.
Slight variations are acceptable due to temperature conditions.
Bench testing of the injectors can only be done using expensive special equipment. Generally this equipment can be found at a dealership and sometimes at a well-equipped machine shop or performance shop. There is no provision for field testing the injectors by the owner/mechanic. DO NOT attempt to test the injector by removing it from the engine and making it spray into a jar.
Never attempt to check a removed injector by hooking it directly to the battery. The injector runs on a much smaller voltage and the 12 volts from the battery will destroy it internally. Since this happens at the speed of electricity, you don't get a second chance.
NOTE: For diagnostic procedures and trouble codes regarding the Electronic Control Module (ECM) and MFI system, refer to Section 4 of this manual.