Circuit Test - Fuel Injector Electrical

FUEL INJECTOR ELECTRICAL CIRCUIT TEST

NOTE: The MFI fuel injector can short internally causing a NO-START condition. The internally shorted injector may not cause a fuse to blow, nor PCM damage. Electrical checks of the system with a Noid Lite or multimeter will indicate the fuel injector wiring harness is okay. A multimeter should be used to check each injector's internal resistance values given in step two of the following procedure. If a multimeter is not available, disconnect one injector's connector at a time and attempt to start the engine. When the engine starts, with one of the connectors off, the faulty fuel injector has been located.

1. Remove all the fuel injector's electrical connector(s).

NOTE: Make sure the multimeter (DVOM) is zeroed before performing a fuel injector electrical resistance check or the reading will be incorrect.

Fuel Injector Resistance Testing:

2. Check resistance of the fuel injector with a multimeter.
^ MFI Injector: 2.0 ± 0.5 ohms at 20°C (68°F)

NOTE: The electrical resistance of an injector will vary depending on temperature. If the resistance is less or greater than 0.5 ohms compared to the others in a MFI fuel system, the fuel injector is probably faulty.

NOTE: Use only the correct Noid Lites when testing an injector harness or terminal damage will occur.

Injector Pulse Detector - Noid Lite:

3. Checking the vehicle electrical harness using a Noid Lite (SA9194E - OTC 7602):
a. Disconnect harness connectors from all injectors, plug Noid Lite into one injector harness connector at a time and turn ignition to the ON position.
b. From passenger compartment, when cranking engine, you'll be able to see:

^ If Noid Lite is flashing while cranking, it indicates normal pulsing voltage in harness. This means electrical system is OK, and problem lies in fuel system.
^ Steady Light or no light at all in Noid Lite indicates electrical malfunction (check electrical diagnostic charts).

NOTE: Noid Lites do not always indicate an electrical circuit is good. The light may always illuminate, but enough current may not be available to pulse the injector. The circuit should always be checked with a good injector unless the Noid Lite doesn't illuminate at all. An injector can be plugged into the electrical circuit and tightly gripped with the hand to confirm pulses when an electrical circuit is suspect.