Hummer H2. Manual - part 1479

Fig. 190: MAF/IAT Sensor & Air Cleaner Assembly 
Courtesy of GENERAL MOTORS CORP. 

1. Loosen the clamp and separate the air cleaner resonator outlet duct from the mass air flow/intake air 

temperature (MAF/IAT) sensor assembly.  

2. Loosen the clamp and separate the air cleaner resonator outlet duct from the throttle body assembly.  

3. Remove the air cleaner resonator outlet duct. 

 

2004 Hummer H2 

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

  

Installation Procedure 

Fig. 191: MAF/IAT Sensor & Air Cleaner Assembly 
Courtesy of GENERAL MOTORS CORP. 

1. Install the air cleaner resonator outlet duct to the throttle body assembly and the MAF/IAT sensor 

assembly.  

2. Tighten the clamps at the throttle body assembly and the MAF/IAT sensor assembly.  

 

2004 Hummer H2 

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

  

DESCRIPTION AND OPERATION

POWERTRAIN CONTROL MODULE (PCM) DESCRIPTION 

Powertrain 

The powertrain has electronic controls to reduce exhaust emissions while maintaining excellent driveability and 
fuel economy. The powertrain control module (PCM) is the control center of this system. The PCM monitors 
numerous engine and vehicle functions. The PCM constantly looks at the information from various sensors and 
other inputs, and controls the systems that affect vehicle performance and emissions. The PCM also performs 
the diagnostic tests on various parts of the system. The PCM can recognize operational problems and alert the 
driver via the malfunction indicator lamp (MIL). When the PCM detects a malfunction, the PCM stores a 
diagnostic trouble code (DTC). The problem area is identified by the particular DTC that is set. The control 
module supplies a buffered voltage to various sensors and switches. Review the components and wiring 
diagrams in order to determine which systems are controlled by the PCM. 

The following are some of the functions that the PCM controls: 

z

The engine fueling  

z

The ignition control (IC)  

z

The knock sensor (KS) system  

z

The evaporative emissions (EVAP) system  

z

The secondary air injection (AIR) system (if equipped)  

z

The exhaust gas recirculation (EGR) system  

z

The automatic transmission functions  

z

The generator  

z

The A/C clutch control  

z

The cooling fan control  

Powertrain Control Module Function 

The powertrain control module (PCM) constantly looks at the information from various sensors and other inputs 
and controls systems that affect vehicle performance and emissions. The PCM also performs diagnostic tests on 
various parts of the system. The PCM can recognize operational problems and alert the driver via the 
malfunction indicator lamp (MIL). When the PCM detects a malfunction, the PCM stores a diagnostic trouble 
code (DTC). The problem area is identified by the particular DTC that is set. The control module supplies a 
buffered voltage to various sensors and switches. The input and output devices in the PCM include analog-to-
digital converters, signal buffers, counters, and output drivers. The output drivers are electronic switches that 
complete a ground or voltage circuit when turned on. Most PCM controlled components are operated via output 
drivers. The PCM monitors these driver circuits for proper operation and, in most cases, can set a DTC 
corresponding to the controlled device if a problem is detected. 

Malfunction Indicator Lamp (MIL) Operation 

The malfunction indicator lamp (MIL) is located in the instrument panel cluster. The MIL will display as either 

 

2004 Hummer H2 

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

  

SERVICE ENGINE SOON or one of the following symbols when commanded ON: 

Fig. 192: Identifying MIL Symbol 
Courtesy of GENERAL MOTORS CORP.

 

2004 Hummer H2 

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