Injector Balance Test (Except 2.2L & 3.4L)

NOTE: Allow engine to cool down to avoid irregular reading due to "hot soak" fuel boiling. To prevent flooding, the fuel injector balance test should not be performed more than once without starting and running engine.

NOTE: If injectors are dirty, they should be cleaned using approved injector cleaning procedure before performing fuel injector balance test.

Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing powertrain diagnostic system check, go to next step.
If engine coolant temperature is greater than 201°F (94°C), go to next step. If engine coolant temperature is less than 201°F (94°C), go to step 4.
Allow engine to cool to less than 201°F (94°C). After engine cools to less than 201°F (94°C), go to next step.
Turn ignition off. Relieve fuel pressure. Install fuel pressure gauge. Turn ignition on with engine off. Install scan tool. Using scan tool, energize fuel pump. Place fuel pressure gauge bleed hose into container. Bleed air out of fuel pressure gauge. Using scan tool, energize fuel pump again. Wait for fuel pressure to build. Observe fuel pressure while fuel pump is running. If fuel pressure reading is 60-66 psi (4.2-4.6 kg/cm² ) on 4.3L, 5.0L and 5.7L, or 55-62 psi (4.0-4.4 kg/cm² ) on 4.8L, 5.3L and 6.0L, go to next step. If fuel pressure reading is not within specification, perform fuel system diagnosis. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
After fuel pump stops, fuel pressure should slightly decrease. If fuel pressure remains constant within 55-60 psi (4.0-4.2 kg/cm² ) on 4.3L, 5.0L and 5.7L, or 48-52 psi (3.4-3.7 kg/cm² ) on 4.8L, 5.3L and 6.0L, go to next step. If fuel pressure reading is not within specification, perform fuel system diagnosis. See appropriate BASIC DIAGNOSTIC PROCEDURES article.

NOTE: Perform step 6 on each injector.

Turn ignition off. Turn ignition on with engine off. Using scan tool, select SPECIAL FUNCTIONS. Select FUEL SYSTEMS, and then INJECTOR BALANCE TEST. Select injector to be tested. Press enter, this will prime fuel pump. After fuel pressure stabilizes, record fuel pressure reading on fuel pressure gauge (first reading). Energize injector by depressing PULSE INJECTOR button on scan tool. Injector will be energized and fuel pressure will decrease. Record fuel pressure reading after fuel pressure stabilizes (second reading). Press enter on scan tool to return to SELECT INJECTOR. Repeat procedure for each injector. Subtract first reading from second reading for each injector (this result is pressure drop value). Add pressure drop value for each injector together and divide total by total number of injectors. If any injector's drop value is greater or less than average drop value by 1.5 psi, replace faulty injector(s) as necessary. If no injector's drop value is greater or less than average drop value by 1.5 psi, perform injector coil test. See INJECTOR COIL TEST (EXCEPT 2.2L & 3.4L) .