Hummer H2. Manual - part 1500

Fig. 1: Fuel Injector Balance Test & Special Tool 
Courtesy of GENERAL MOTORS CORP. 

Callouts For Fig. 27 

Fuel Injector Balance Test Example (Typical) 

Test Description 

The numbers below refer to the step numbers on the diagnostic table. 

6: If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop 
value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by 
subtracting the second pressure reading from the first pressure reading. Refer to the illustration above.  

Fuel Injector Balance Test with Special Tool 

Callout

Component Name

1

First Fuel Pressure Gauge Reading

2

Second Fuel Pressure Gauge Reading

Cylinder

1

2

3

4

1st Reading

296 kPa 

(43 psi)

296 kPa (43 psi)

296 kPa 

(43 psi)

296 kPa (43 psi)

2nd Reading

131 kPa 

(19 psi)

117 kPa (17 psi)

124 kPa 

(18 psi)

145 kPa (21 psi)

Amount of Drop

165 kPa 

(24 psi)

179 kPa (26 psi)

172 kPa 

(25 psi)

151 kPa (22 psi)

Average Range: 156-176 

kPa (22.5-25.5 psi)

Injector 

OK

Replace fuel injector - too 

much fuel pressure drop

Injector 

OK

Replace fuel injector - too 

little fuel pressure drop

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

  

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics 
Connector End View Reference: Engine Controls Connector End Views or Powertrain Control 
Module (PCM) Connector End Views

1

Did you perform the Diagnostic System Check - 
Engine Controls?

-

Go to Step 2

Go to 

Diagnostic 

System Check - 

Engine 

Controls

2

Did you perform the Fuel Injector Coil Test?

-

Go to Step 3

Go to Fuel 

Injector Coil 

Test

3

Observe the ECT Sensor parameter with a scan 
tool.Is the ECT Sensor parameter less than the 
specified value?

IMPORTANT:

Do not perform this test if the engine coolant 
temperature (ECT) is above 94°C (201°F).

94°C (201°F)

Go to Step 4

-

4

1. Turn OFF the ignition.  

2. Install the fuel pressure gauge. Refer to 

Fuel Pressure Gauge Installation and 
Removal .  

3. Turn ON the ignition, with the engine OFF. 

4. Command the fuel pump ON with a scan 

tool. 

5. Observe the fuel pressure gauge, with the 

fuel pump commanded ON.  

Is the fuel pressure within the specified range?

IMPORTANT:

Verify there is adequate fuel in the fuel tank 
before proceeding with this diagnostic.

IMPORTANT:

z

You may need to command the fuel 
pump ON a few times, in order to 
obtain the highest possible fuel 
pressure.  

z

Do not start the engine.  

385-425 kPa 

(55-62 psi) 

VIN: (V, T, 

U) Gasoline

335-375 kPa 

(48-54 psi) 

VIN Z 

Ethanol

Go to Step 5

Go to Fuel 

System 

Diagnosis

IMPORTANT:

The fuel pressure may vary slightly when the 

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

  

5

Monitor the fuel pressure gauge for 1 
minute.Does the fuel pressure drop more than the 
specified value?

fuel pump stops operating. After the fuel pump 
stops operating, the fuel pressure should 
stabilize and remain constant.

34 kPa (5 psi)

Go to Fuel 

System 

Diagnosis

Go to Step 6

6

1. Connect the J 39021 Fuel Injector Coil and 

Balance Tester and the J 39021-380 Fuel 
Injector Test Harness to a fuel injector.  

2. Set the amperage supply selector switch on 

the fuel injector tester to the Balance Test 
0.5-2.5 amp position.  

3. Command the fuel pump ON and OFF with 

a scan tool. 

4. Record the fuel pressure indicated by the 

fuel pressure gauge after the fuel pressure 
stabilizes. This is the first pressure reading. 

5. Energize the fuel injector by depressing the 

Push to Start Test button on the fuel 
injector tester.  

6. Record the fuel pressure indicated by the 

fuel pressure gauge. This is the second fuel 
pressure reading.  

7. Repeat steps 1-6 for each fuel injector.  

8. Subtract the second pressure reading from 

the first pressure reading for one fuel 
injector. The result is the pressure drop 

NOTE:

Do Not repeat any portion of this test before 
running the engine in order to prevent the 
engine from flooding.

IMPORTANT:

Refer to the illustration in the supporting text 
when performing the following steps.

IMPORTANT:

Record the fuel pressure value 
immediately after the fuel injector stops 
pulsing. The fuel pressure may rise after 
the fuel injector stops pulsing. Do not 
record the higher fuel pressure value.

10 kPa (1.5 

psi)

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

  

FUEL INJECTOR BALANCE TEST WITH TECH 2 

Description 

The scan tool is first used to energize the fuel pump. The scan tool is then used to pulse each injector for a 
precise amount of time, allowing a measured amount of fuel into the manifold. This causes a drop in system 
fuel pressure that can be recorded and used to compare the flow through each injector. 

Fuel Injector Balance Test Example (Typical) 

Test Description 

The numbers below refer to the step numbers on the diagnostic table. 

5: If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop 
value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by 

value.  

9. Obtain a pressure drop value for each fuel 

injector.  

10. Add all of the individual pressure drop 

values. This is the total pressure drop.  

11. Divide the total pressure drop by the 

number of fuel injectors. This is the 
average pressure drop.  

Does any fuel injector have a pressure drop value 
that is more than the average pressure drop or less 
than the average pressure drop by the specified 
value?

Go to Step 7

Go to 

Symptoms - 

Engine 

Controls

7

Perform the Fuel Injector Cleaning Procedure .
Did you complete the procedure?

-

Go to Step 8

-

8

Operate the vehicle in order to verify the repair. 
Does a driveability condition still exist?

-

Go to 

Symptoms - 

Engine 

Controls

System OK

Cylinder

1

2

3

4

1st Reading

296 kPa 

(43 psi)

296 kPa (43 psi)

296 kPa 

(43 psi)

296 kPa (43 psi)

2nd Reading

131 kPa 

(19 psi)

117 kPa (17 psi)

124 kPa 

(18 psi)

145 kPa (21 psi)

Amount of Drop

165 kPa 

(24 psi)

179 kPa (26 psi)

172 kPa 

(25 psi)

151 kPa (22 psi)

Average Range: 156-176 

kPa (22.5-25.5 psi)

Injector 

OK

Replace fuel injector - too 

much fuel pressure drop

Injector 

OK

Replace fuel injector - too 

little fuel pressure drop

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2