Hummer H2. Manual — part 1497

Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 30

Go to Step 15

15

Test the battery positive voltage bus bar circuit of the
underhood junction block between the 40-amp IGN B fuse
and the ignition switch for a short to ground.
Did you find a condition?

Go to Step 29

Go to Step 16

16

Test the ignition 1 voltage bus bar circuit of the underhood
junction block that contains the ignition relay for a short to
ground.
Did you find a condition?

Go to Step 29

Go to Step 27

17

1. Turn OFF the ignition.

2. Probe the mounting stud for the battery positive cable

at the underhood junction block with a test lamp that
is connected to a good ground. Refer to Probing
Electrical Connectors and Troubleshooting with a
Test Lamp in Wiring Systems.

Does the test lamp illuminate?

Go to Step 29

Go to Diagnostic

System Check -

Engine Electrical

in Engine
Electrical

18

1. Turn OFF the ignition.

2. Remove the ignition relay with the J 43244 from the

underhood junction block. Refer to Relay
Replacement (Within an Electrical Center) or
Relay Replacement (Attached to Wire Harness) in
Wiring Systems.

3. Probe the battery positive voltage circuit of the

ignition relay at the underhood junction block with a
test lamp that is connected to a good ground. Refer to
Probing Electrical Connectors and
Troubleshooting with a Test Lamp in Wiring
Systems.

Does the test lamp illuminate?

NOTE:

Refer to Test Probe Notice in Cautions and
Notices.

Go to Step 19

Go to Step 29

19

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

2. Probe the ignition 1 voltage circuit of the ignition

relay at the underhood junction block with a test
lamp that is connected to a good ground. Refer to
Probing Electrical Connectors and
Troubleshooting with a Test Lamp in Wiring
Systems.

2004 Hummer H2

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

Does the test lamp illuminate?

Go to Step 23

Go to Step 20

20

1. Turn OFF the ignition.

2. Test the ignition 1 voltage circuit between the

ignition switch and the underhood junction block for
a high resistance or for an open. Refer to Circuit
Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 30

Go to Step 21

21

Test the ignition switch assembly for a high resistance or
for an open. Refer to Circuit Testing in Wiring Systems.
Did you find a condition?

Go to Step 28

Go to Step 22

22

Test the battery positive voltage circuit between the
ignition switch and the underhood junction block for a high
resistance or for an open. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 30

Go to Step 29

23

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

2. Probe the coil ground circuit of the ignition relay at

the underhood junction block with a test lamp that is
connected to battery voltage. Refer to Probing
Electrical Connectors and Troubleshooting with a
Test Lamp in Wiring Systems.

Does the test lamp illuminate?

Go to Step 25

Go to Step 24

24

1. Turn OFF the ignition.

2. Disconnect the negative battery cable at the battery.

Refer to Battery Negative Cable
Disconnect/Connect Procedure (Single Battery) in
Engine Electrical.

3. Disconnect the underhood junction block electrical

connectors.

4. Test the coil ground circuit of the ignition relay at the

underhood junction block electrical connector for a
high resistance or for an open. Refer to Circuit
Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 30

Go to Step 29

1. Turn OFF the ignition.

2. Jumper the ignition relay battery positive voltage

circuit and the ignition relay load circuit together at
the underhood junction block with a 20-amp fused
jumper wire. Refer to Using Fused Jumper Wires in
Wiring Systems.

2004 Hummer H2

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

FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS

Circuit Description

25

3. Probe the following fuses with a test lamp that is

connected to a good ground:

z

PCM 1

z

ETC/ECM

z

INJ 1

z

INJ 2

z

SBA, if equipped.

Refer to Probing Electrical Connectors and
Troubleshooting with a Test Lamp in Wiring
Systems.

Does the test lamp illuminate on at least one test point of
each fuse?

Go to Step 26

Go to Step 29

26

Test for an intermittent and for a poor connection at the
underhood junction block, ignition relay connector
location. Refer to Testing for Intermittent Conditions
and Poor Connections in Wiring Systems.
Did you find a condition?

Go to Step 29

Go to Step 27

27

Replace the ignition relay. Refer to Relay Replacement
(Within an Electrical Center) or Relay Replacement
(Attached to Wire Harness) in Wiring Systems.
Did you complete the replacement?

Go to Step 30

-

28

Replace the ignition switch. Refer to Ignition Switch
Replacement in Steering Wheel and Column.
Did you complete the replacement?

Go to Step 30

-

29

Replace the underhood electrical center. Refer to
Underhood Electrical Center or Junction Block
Replacement in Wiring Systems.
Did you complete the replacement?

Go to Step 30

-

30

1. Replace any open fuses.

2. Turn OFF the ignition for 30 seconds.

3. Attempt to start the engine.

Does the engine start and run?

Go to Step 31

Go to Engine

Cranks but Does

Not Run

31

1. Clear the DTCs with a scan tool.

2. Operate the vehicle for 5 minutes.

Does a DTC set during this ignition cycle?

Go to Diagnostic

Trouble Code

(DTC) List

System OK

2004 Hummer H2

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

The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will
disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The
control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The
control module disables the fuel pump relay within two seconds if ignition reference pulses cease to be detected
and the ignition remains ON.

Diagnostic Aids

A fuel pump prime terminal is located at the underhood bussed electrical center (UBEC). Refer to the UBEC
cover for terminal location.

The following conditions may have caused the fuel pump fuse to open:

z

A faulty fuse

z

An intermittent short in the fuel pump power supply circuit

z

An intermittent internal component failure

For an intermittent condition, refer to Intermittent Conditions .

Test Description

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

3: This step determines if the condition is located on the coil side or on the switch side of the fuel pump
relay.

4: This step verifies that the powertrain control module (PCM) is providing voltage to the fuel pump
relay.

5: This step tests for an open in the ground circuit to the fuel pump relay.

6: This step determines if a voltage is constantly being applied to the fuel pump relay.

13: This step determines if the condition with the circuit is intermittent.

Fuel Pump Electrical Circuit Diagnosis

Step

Action

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

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

2. Command the fuel pump relay ON and OFF with a scan

tool.

Does the fuel pump turn ON and OFF when commanded with a

Go to

Diagnostic

2004 Hummer H2

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