Hummer H2. Manual — part 1494

MALFUNCTION INDICATOR LAMP (MIL) INOPERATIVE

Circuit Description

Voltage is supplied directly to the malfunction indicator lamp (MIL). The powertrain control module (PCM)
turns the MIL ON by grounding the MIL control circuit. There should be a steady MIL with the ignition ON
and the engine OFF.

MIL Operation

The MIL is located on the instrument panel cluster (IPC).

MIL Function

z

The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service
as soon as possible.

z

The MIL illuminates during a bulb test and a system test.

procedures.

Additional
Inspections

z

Visually and physically inspect the vacuum hoses for splits, kinks, and proper
connections and routing as shown on the Vehicle Emission Control Information
label.

z

Inspect the intake manifold and the exhaust manifold passages for casting flash.

z

Inspect the transmission torque converter clutch (TCC) operation. The scan tool
should indicate an RPM drop when the TCC is commanded ON. Refer to
Diagnostic System Check - Automatic Transmission in Automatic
Transmission - 4L60-E.

z

Inspect the exhaust system for possible restrictions. Inspect the following:

{

Inspect the exhaust system for damaged or collapsed pipes.

{

Inspect the mufflers for heat distress or possible internal failure.

{

Inspect for possible plugged catalytic converters. Refer to Restricted
Exhaust in Engine Exhaust.

z

Electromagnetic interference (EMI) on the reference circuit can cause an engine
miss condition. A scan tool can usually detect EMI by monitoring the engine
RPM. A sudden increase in RPM with little change in actual engine RPM change
may indicate that EMI is present. If a problem exists, inspect for high voltage
components near the ignition control circuits.

z

Inspect the park/neutral position (PNP) switch operation. Refer to Park/Neutral
Position Switch Adjustment in Automatic Transmission - 4L60-E.

z

Inspect for faulty motor mounts. Refer to Engine Mount Inspection in Engine
Mechanical.

z

Inspect the intake manifold and the exhaust manifold passages for casting flash

2004 Hummer H2

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

z

A DTC will be stored if a MIL is requested by the PCM.

MIL Illumination

z

The MIL will illuminate with ignition switch ON and the engine not running.

z

The MIL will turn OFF when the engine is started.

z

The MIL will remain ON if the self-diagnostic system has detected a malfunction.

z

The MIL may turn OFF if the malfunction is not present.

z

If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the
ignition switch is ON.

z

If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is
cycled OFF, then ON.

Test Description

The number below refers to the step number on the diagnostic table.

4: This step tests for a short to voltage on the MIL control circuit. With the fuse removed there should be
no voltage on the MIL control circuit.

Malfunction Indicator Lamp (MIL) Inoperative

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Component 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. Verify whether the instrument cluster is

operational. If the instrument panel (IP) is
completely inoperative, refer to Diagnostic
System Check - Instrument Cluster in
Instrument Panel, Gauges and Console.

2. Command the MIL ON and OFF with a scan

tool.

Does the MIL turn ON and OFF when commanded
with a scan tool?

-

Go to

Intermittent

Conditions

Go to Step 3

3

Inspect the fuse that supplies voltage to the MIL.
Is the fuse open?

-

Go to Step 10

Go to Step 4

1. Turn OFF the ignition.

2. Remove the fuse that supplies voltage to the

MIL.

2004 Hummer H2

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

4

3. Disconnect the powertrain control module

(PCM).

4. Turn ON the ignition with the engine OFF.

5. Measure the voltage from the MIL control

circuit in the PCM harness connector to a
good ground.

Is the voltage less than the specified value?

0.3 V

Go to Step 5

Go to Step 11

5

1. Turn OFF the ignition.

2. Install the fuse that supplies voltage to the

MIL.

3. Turn ON the ignition with the engine OFF.

4. Connect a 3-amp fused jumper wire between

the MIL control circuit in the PCM harness
connector and a good ground.

Is the MIL illuminated?

-

Go to Step 9

Go to Step 6

6

1. Turn OFF the ignition.

2. Remove the instrument panel cluster (IPC).

Refer to Instrument Panel Cluster (IPC)
Replacement in Instrument Panel, Gauges,
and Console.

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

4. Probe the MIL voltage supply circuit of the

IPC harness connector with a test lamp that is
connected to a good ground.

Does the test lamp illuminate?

-

Go to Step 7

Go to Step 12

7

Test the MIL control circuit for an open or high
resistance. Refer to Circuit Testing and Wiring
Repairs in Wiring Systems.
Did you find and correct a condition?

-

Go to Step 15

Go to Step 8

8

Test for an intermittent and for a poor connection at
the IPC. Refer to Testing for Intermittent
Conditions and Poor Connections and Connector
Repairs in Wiring Systems.
Did you find and correct the condition?

-

Go to Step 15

Go to Step 13

9

Test for an intermittent and for a poor connection at
the PCM. Refer to Refer to Testing for
Intermittent Conditions and Poor Connections
and Connector Repairs in Wiring Systems.
Did you find and correct the condition?

-

Go to Step 15

Go to Step 14

Repair the short to ground in the voltage supply

2004 Hummer H2

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

MALFUNCTION INDICATOR LAMP (MIL) ALWAYS ON

Circuit Description

Voltage is supplied directly to the malfunction indicator lamp (MIL). The powertrain control module (PCM)
turns the MIL ON by grounding the MIL control circuit.

MIL Operation

The MIL is located on the instrument panel (IPC).

MIL Function

z

The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service
as soon as possible.

z

The MIL illuminates during a bulb test and a system test.

z

A DTC will be stored if a MIL is requested by the diagnostic.

MIL Illumination

10

circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?

-

Go to Step 15

-

11

Repair the short to voltage in the MIL control
circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?

-

Go to Step 15

-

12

Repair the open in the MIL voltage supply circuit.
Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?

-

Go to Step 15

-

13

Replace the IPC. Refer to Instrument Panel
Cluster (IPC) Replacement in Instrument Panel,
Gauges, and Console.
Did you complete the replacement?

-

Go to Step 15

-

14

Replace the PCM. Refer to Powertrain Control
Module (PCM) Replacement .
Did you complete the replacement?

-

Go to Step 15

-

15

1. Turn OFF the ignition for 30 seconds.

2. Start the engine.

3. Observe the MIL.

Does the MIL operate correctly?

-

Go to Step 16

Go to Step 2

16

Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?

-

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