Hummer H2. Manual - part 353

Fig. 125: Adhesive Strip To Body 
Courtesy of GENERAL MOTORS CORP. 

4. Carefully align adhesive strip to body and pull exposed tape lead down.  

5. Apply approximately 30 psi to tail lamp guard to adhere guard to the body.  

6. Close the liftgate.  

DESCRIPTION AND OPERATION

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2

  

EXTERIOR LIGHTING SYSTEMS DESCRIPTION AND OPERATION

Exterior Lamps 

The exterior lighting system consists of the following lamps: 

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The headlamps  

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The daytime running lamps (DRL)  

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The park, tail and marker lamps  

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The turn signal lamps  

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The stop lamps  

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The backup lamps  

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The clearance lamps  

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The off-road lamps  

Headlamps 

With automatic lamp control (ALC) the headlamps may be turned on in 3 different ways. Some export vehicles 
are not equipped with ALC, disabling the ALC, DRL, and wiper activated headlamp (WAH) functions in the 
module. With ALC disabled, the headlamps will operate in the manual mode. In these vehicle diagnostics the 
term AUTO shall be equivalent to OFF when referencing headlamp switch positions. First, when the driver 
places the headlamp switch in the ON position, for normal operation. Second, with the headlamp switch placed 
in the AUTO position, for ALC. During ALC, the headlamps will be in daytime running lamp (DRL) operation 
in daylight conditions, or headlamp operation in low light conditions. Third, in WAH mode. Only when the 
wiper system is activated while the vehicle is in gear, the wiper blades have completed at least 3 cycles, and a 
35 second time period expires, will the body control module (BCM) switch from DRL mode to headlamp mode 
during daylight conditions. When the gearshift lever is placed in the PARK or NEUTRAL position or if the 
wipers are turned off, normal manual, or ALC operation will resume after approximately 60 seconds 

Headlamp ON/OFF control is determined by the BCM by a signal on the headlamp switch on input circuit when 
the headlamp switch is in the ON position. When the headlamp switch is in the AUTO position, the BCM 
determines headlamps ON/OFF by the voltage from the ambient light sensor. 

The BCM will also illuminate the headlamps and park lamps after the front wipers have been turned ON. The 
windshield wiper module signals the BCM on the windshield wiper switch signal 2 circuit when the windshield 
wipers are ON. 

The high beam headlamps receive voltage from the headlamp high relay located in the underhood fuse block. 
The BCM controls the relay on the headlamp high beam relay control circuit. High beam control is determined 
by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp 
dimmer switch signal circuit is grounded, the BCM grounds the headlamp high beam relay control circuit, 
illuminating the high beam headlamps. The right and left high beam circuits are independent and are fused 
independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G104. 

The low beam headlamps receive voltage from the headlamp low relay located in the underhood fuse block. The 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2

  

BCM controls the relay on the headlamp low beam relay control circuit. Low beam control is determined by a 
signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp 
dimmer switch signal circuit is open, the BCM grounds the headlamp low beam relay control circuit, 
illuminating the low beam headlamps. The right and left low beam circuits are independent and are fused 
independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G104. 

If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the 
headlamps approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places 
the headlamp switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch 
is in the ACCY position, the headlamps will remain on until turned off, or the battery runs dead. 

The high beam indicator is illuminated when the instrument cluster receives a class 2 serial data message from 
the BCM that the high beams are illuminated. 

Daytime Running Lamps (DRL) 

The daytime running lamps (DRL) will operate when the ignition switch is in the RUN position, the gear 
selector is not in the PARK position, and the headlamp switch is in the AUTO position. When these conditions 
have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate. Some export 
vehicles are not equipped with automatic lamp control (ALC), disabling the ALC, DRL and wiper activated 
headlamp (WAH) functions in the module. With ALC disabled, the headlamps will operate in the manual mode. 
In these vehicle diagnostics, the term AUTO shall be equivalent to OFF when referencing headlamp switch 
positions. 

The ambient light sensor is a light sensitive transistor that varies its voltage signal to the body control module 
(BCM) in response to changes to the outside (ambient) light level. When the BCM receives this signal it will 
either turn on the DRL or the headlamps for auto headlamp operation. Any function or condition that turns on 
the headlamps will cancel the DRL operation. The DRL can be manually turned OFF by depressing the 
AHL/DRL defeat switch in the headlamp switch. The AHL/DRL defeat switch sends a ground signal through 
the DRL switch signal circuit to the BCM. The BCM then turns OFF the DRL. When the AHL/DRL are 
manually turned OFF at the headlamp switch, the AHL/DRL will default to ON with the next ignition cycle. 
The DRL are separate lamps independent of the headlamps. With the headlamp switch in the AUTO position, 
the DRL will either be turned ON or OFF, after an approximate 8 second delay depending on whether daylight 
or low light conditions are sensed. The DRL 10 A fuse in the underhood fuse block supplies battery positive 
voltage to the DRL relay switch contacts and relay coil. When the BCM energizes the DRL relay on the DRL 
relay control circuit in daylight conditions, the DRL receives voltage on the DRL supply voltage circuit. 
Ground for the DRL is at G100. 

Park, Tail and Marker Lamps 

The park, tail, and marker lamps, including the license lamps, are turned on when the headlamp switch is placed 
in the PARK or ON position, or anytime the headlamps are requested. The underhood fuse block supplies 
battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The body 
control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the park 
lamps are turned on the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the FR 
PRK 10 A fuse, RR PRK 10 A fuse, LR PRK 10 A fuse, and the TRL PRK 10 A fuse, and to their respective 
park and marker lamps. The front park and marker lamps are grounded at G100. The rear park and marker 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2

  

lamps are grounded at G401. The license lamps are grounded at G410. If the headlamp switch is left in the ON 
position, the inadvertent power control feature will turn off the park, tail, and marker lamps, approximately 10 
minutes after the ignition switch is turned to the OFF position. If the driver places the headlamp switch in the 
ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the 
park, tail and marker lamps will remain on until turned off or the battery runs dead. 

Turn Signal Lamps 

The IGN E 10 A fuse in the underhood fuse block supplies battery positive voltage to the turn signal/hazard 
switch assembly. The FLASH 25 A fuse in the I/P fuse block supplies battery positive voltage to the turn 
signal/flasher module and ground is supplied at G200. When the turn signal switch is placed in either the left or 
right position, the circuit is complete from the turn signal switch to the turn sign/flasher module. The turn 
sign/flasher module then sends an on-off voltage signal through the LT TRLR, RT TRLR, LT TURN or RT 
TURN FUSES in the I/P fuse block to the appropriate turn signal. The instrument panel cluster (IPC) indicators 
also receive voltage from the LT TURN and RT TURN fuses. The audio chime is also activated when the turn 
signals are on. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn 
indicators. The front turn signals are grounded at G100. The rear turn signals are grounded at G401. 

Stop Lamps 

The STOP LP 25 A fuse in the underhood fuse block supplies battery positive voltage to the normally open stop 
lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is 
supplied to both the STOP 15 A fuse and the CHMSL 10 A fuse in the IP fuse block, and to the turn signal 
switch. The turn signal/hazard module then supplies voltage to both of the trailer rear turn/stop lamp supply 
voltage circuits. The voltage from the CHMSL 10 A fuse is to the center high mounted stop lamp (CHMSL) 
and the trailer jumper harness. The voltage from the STOP 15 A fuse is to the stop lamps, throttle actuator 
control (TAC) module, and the electronic brake control module (EBCM). The CHMSL is grounded at G410. 
The stop lamps are grounded at G401. 

Backup Lamps 

The backup lamp request signal is sent from the powertrain control module (PCM) to the body control module 
(BCM) on the class 2 message system. This signal is based on the park neutral position (PNP) switch signal. 
The BCM supplies voltage on the backup lamp supply voltage circuit to the backup lamps and to the automatic 
day/night mirror. Voltage for the courtesy lamp supply voltage circuit and backup lamp supply voltage circuit is 
from the TBC B fuse in the instrument panel fuse block directly through the BCM to these circuits. A short to 
ground on either of these circuits will open the fuse. The backup lamps are grounded at G401. 

For trailer wiring, a separate backup lamp circuit is connected through the underhood fuse block from the TRLR 
B/U 10 A fuse to the trailer wiring harness. 

Clearance Lamps 

The clearance lamps, are turned on when the headlamp switch is placed in the PARK or ON position or anytime 
the headlamps are requested. The underhood fuse block supplies battery positive voltage to both the park lamp 
relay switch contacts and the park lamp coil circuit. The body control module (BCM) provides a ground or 
control circuit to the park lamp relay coil circuit. When the park lamps are turned on the BCM energizes the 
park lamp relay. Current flow is from the park lamp relay to the INT PRK 10 A fuse, and to the clearance and 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Lighting Systems - Hummer H2