Disconnect injector solenoid connector. Measure resistance across solenoid terminals. Resistance should be at least 1.2 ohms.
If resistance is less than 1.2 ohms, replace injector, and ensure fuse in circuit No. 439 (Red/White/Black wire) is not blown. Check for 12 volts on circuit No. 439 with ignition on. See Fig 1 . Ensure fuel pressure at injector is 9-13 psi (.6-.9 kg/cm² ). See FUEL PRESSURE in BASIC TESTING article in this section.
With injector connector disconnected, crank engine. If injector sprays or drips fuel, replace injector or injector "O" ring. Connect a fuel injector test light to injector connector, and crank engine. If test light blinks, reconnect harness to injector, and crank engine.
If fuel injector tester does not blink, check for short to ground in ECM circuit D9-D10 (peak and hold jumper). See Fig 1 . If short is present, repair circuit or replace ECM. With ignition on and if both terminals on fuel injector test light are off, repair open in circuit No. 439. If both terminals on fuel injector test light are on, repair short to voltage in circuit No. 467.

Fig 1: Identifying Injector & Ignition System Circuits

Courtesy of GENERAL MOTORS CORP.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Fuel Injector Solenoid