Hummer H2. Manual — part 1496

IGNITION RELAY DIAGNOSIS

Circuit Description

The ignition relay is a normally open relay. The relay armature is held in the open position by spring tension.
When the ignition switch is turned to the run or start position, current will flow through the relay coil. A wire
connected to the other end of the relay coil completes the path to ground. The electromagnetic field created by
the relay coil, overcomes the spring tension and moves the armature allowing the relay contacts to close. The
closed relay contacts allow current to flow from the battery to the following fuses:

z

PCM 1

z

ETC/ECM

z

INJ 1

z

INJ 2

z

SBA, if equipped.

When the ignition switch is turned to the OFF position, the electromagnetic field collapses. This action allows
the spring tension to move the armature away from the relay contacts, which interrupts current flow to the fuses.

If the ignition relay fails to close, the engine will crank, but will not run. The class 2 communications will be
available with the use of a scan tool.

The ignition relay table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test
(Non-HP2) in Engine Electrical.

Ignition Relay Diagnosis

Did you complete the replacement?

Go to Step 13

-

13

1. Clear the DTCs with a scan tool.

2. Turn OFF the ignition for 30 seconds.

3. Attempt to start the engine.

Does the engine start the continue to run?

-

Go to Step 14

Go to Step 2

14

1. Allow the engine to reach operating

temperature.

2. Observe the DTC information with a scan

tool.

Are there any DTCs that have not been diagnosed?

-

Go to

Diagnostic

Trouble Code

(DTC) List

System OK

Step

Action

Yes

No

Schematic Reference: Power Distribution Schematics and Ground Distribution Schematics in
Wiring Systems and Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Powertrain Control

2004 Hummer H2

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

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. Remove the underhood junction block cover.

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 3

Go to Step 10

3

1. Turn OFF the ignition.

2. Probe both test points of the PCM 1 fuse 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 on either test point of the
fuse?

Go to Step 4

Go to Step 30

4

1. Turn OFF the ignition.

2. Remove the ignition relay from the underhood

junction block with the J 43244 Relay Puller Pliers.
Refer to Relay Replacement (Within an Electrical
Center) or Relay Replacement (Attached to Wire
Harness) in Wiring Systems.

3. 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

NOTE:

Refer to Test Probe Notice in Cautions and
Notices.

2004 Hummer H2

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

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

Does the test lamp illuminate?

Go to Step 7

Go to Step 5

5

Test the relay load bus bar of the underhood junction block
between the ignition relay and the fuses to the circuit
components for a short to battery positive voltage. Refer to
Circuit Testing in Wiring Systems.
Did you find a condition?

Go to Step 29

Go to Step 6

6

1. Turn OFF the ignition.

2. Remove the following fuses from the underhood

junction block:

z

PCM 1

z

ETC/ECM

z

INJ 1

z

INJ 2

z

SBA, if equipped.

3. Probe the above fuse terminals in 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 at any of the fuse terminals?

Go to Diagnostic

System Check -

Engine Electrical

in Engine
Electrical

Go to Step 27

7

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

connector that contains the ignition 1 voltage circuit
for the ignition relay.

4. Disconnect the ignition switch electrical connector

that contains the ignition 1 voltage circuit for the
ignition relay.

5. Connect the negative battery cable to the battery.

6. Test the ignition 1 voltage circuit for a short to

battery positive voltage. Refer to Circuit Testing
and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 30

Go to Step 8

2004 Hummer H2

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

8

1. Turn OFF the ignition.

2. Probe the ignition 1 voltage terminal on the ignition

switch side of the ignition switch electrical connector
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 28

Go to Step 9

9

Test the ignition 1 voltage bus bar circuit in the underhood
junction block for a short to battery positive voltage. Refer
to Circuit Testing in Wiring Systems.
Did you find a condition?

Go to Step 29

Go to Step 27

10

1. Turn OFF the ignition.

2. Inspect the 40-amp IGN B fuse in the underhood

junction block. Refer to Circuit Protection - Fuses
in Wiring Systems.

Is the fuse open?

Go to Step 11

Go to Step 18

11

1. Remove the 40-amp IGN B fuse from the underhood

junction block.

2. Probe both fuse terminals in 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 on at least one fuse terminal?

NOTE:

Refer to Test Probe Notice in Cautions and
Notices.

Go to Step 12

Go to Step 17

12

Test the ignition 1 voltage circuit between the ignition
switch and the underhood junction block for a short to
ground. Refer to Circuit Testing and Wiring Repairs in
Wiring Systems.
Did you find and correct the condition?

Go to Step 30

Go to Step 13

13

Test the ignition switch assembly for a short to ground.
Refer to Circuit Testing in Wiring Systems.
Did you find a condition?

Go to Step 28

Go to Step 14

14

Test the battery positive voltage circuit between the
underhood junction block and the ignition switch for a
short to ground. Refer to Circuit Testing and Wiring

2004 Hummer H2

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