Hummer H2. Manual - part 1594

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