Hummer H2. Manual — part 1381

Fig. 2: RR Of Engine Compartment Component Views
Courtesy of GENERAL MOTORS CORP.

Callouts For Fig. 2

COOLING SYSTEM CONNECTOR END VIEWS

Coolant Level Terminal Identification Switch (If Equipped)

Callout

Component Name

1

A/C Low Pressure Switch

2

A/C Accumulator

3

Intake Air Temperature (IAT)/Mass Air Flow (MAF) Sensor

4

Coolant Level Switch (If Equipped)

2004 Hummer H2

2004 ENGINE Engine Cooling - Hummer H2

DIAGNOSTIC INFORMATION AND PROCEDURES

DIAGNOSTIC STARTING POINT - ENGINE COOLING

Begin the system diagnosis with the Diagnostic System Check - Engine Cooling . The Diagnostic System
Check will provide the following information:

z

The identification of the control module(s) which command the system.

z

The ability of the control module(s) to communicate through the serial data circuit.

z

The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and
where the procedure is located.

DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING

Test Description

The numbers below refer to the step numbers on the diagnostic table.

3: Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a
total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular
condition.

Connector Part Information

z

12052644

z

2-Way F Metri-Pack 150 Series Sealed (GY)

Pin

Wire Color

Circuit No.

Function

A

L-GN

1478

Coolant Level Switch Signal

B

BK

550

Ground

2004 Hummer H2

2004 ENGINE Engine Cooling - Hummer H2

4: Determine if the Instrument Cluster or Powertrain Control Modules have set DTCs which may affect
Engine Cooling operation are present.

5: The presence of DTCs which begin with "U" indicate some other module is not communicating. The
specified procedure will compile all the available information before tests are performed.

Diagnostic System Check - Engine Cooling

SCAN TOOL OUTPUT CONTROLS

Instrument Cluster

Step

Action

Yes

No

1

Did you review a Diagnostic
Starting Point-Engine Cooling?

Go to Step 2

Go to Diagnostic Starting

Point - Engine Cooling

2

Install a scan tool.
Does the scan tool power up?

Go to Step 3

Go to Scan Tool Does Not

Power Up in Data Link

Communications

3

1. Turn ON the ignition, with

the engine OFF.

2. Attempt to establish

communication with the
following control modules:

z

The instrument cluster

z

The powertrain control
module

Does the scan tool communicate
with the control modules?

Go to Step 4

Go to Scan Tool Does Not

Communicate with Class 2

Device in Data Link

Communications

4

Select the powertrain control
module display DTCs function on
the scan tool.
Does the scan tool display any
DTCs?

Go to Step 5

Go to Symptoms - Engine

Cooling

5

Does the scan tool display any
DTCs which begin with a "U"?

Go to Scan Tool Does Not

Communicate with Class 2

Device in Data Link

Communications

Go to Step 6

6

Does the scan tool display any
DTCs that are associated with the
Engine Cooling System?

Go to Diagnostic Trouble

Code (DTC) List

Go to Diagnostic Trouble

Code (DTC) List in Engine

Controls - 4.8L, 5.3L, and 6.0L

Scan Tool Output

Control

Additional Menu

Selection(s)

Description

Special Functions

Lamp Test

Command the instrument cluster to illuminate all
lamps in the cluster

Special Functions

IPC Gauges

Command the instrument cluster to sweep all gauges.

2004 Hummer H2

2004 ENGINE Engine Cooling - Hummer H2

SCAN TOOL DATA LIST

Instrument Panel Cluster (IPC)

6.0L

SCAN TOOL DATA DEFINITIONS

Coolant Level Switch - Range: Low/OK

This parameter indicates when the engine coolant level is low. The scan tool displays Low when the
powertrain control module (PCM) detects the engine coolant level switch is open.

ECT - Range: -40° C to +150° C (-40° F to +302° F)

The PCM applies 5.0 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal
resistance as the engine temperature changes. When the sensor is cold (internal resistance high), the PCM
senses a high signal voltage and interprets the voltage as a cold engine. As the sensor warms (internal
resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm
engine.

Displayed Coolant Temperature - Range: 32-127° C (89-260° F)

This data is the coolant temperature the Instrument Cluster is attempting to display on the coolant
temperature gauge. This data may differ from the monitored coolant temperature for a period of time due
to filtering. The data may also differ from the monitored coolant temperature when coolant temperature is
not in the range of 71-127° C (160-260° F) since the display is limited to these values. If a class 2
communication failure occurs, this data will be at the minimum value of 32° C (89° F).

Special Functions

Segment Tests

Command the instrument cluster message center to
display all segments.

Scan Tool

Parameter

Data

List

Units Displayed

Typical Data Value

Ignition Switch in RUN/Engine running/Automatic Transmission in PARK/Manual Transmission

in NEUTRAL/Air Conditioner is OFF

Displayed Coolant

Temp

Data

Celsius (C)/Fahrenheit

(F)

87° C (189° F)

Monitored Coolant

Temp

Data

Celsius (C)/Fahrenheit

(F)

87° C (Fluctuates range 82-93° C) 189° F

(Fluctuates range 180-200° F)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition Switch in RUN/Engine running/Automatic Transmission in PARK/Manual Transmission

in NEUTRAL/Air Conditioner is OFF

ECT Sensor

Engine Data 1
Engine Data 2

Degrees

87° C (189° F)

Coolant Level Switch

Engine Data 2

Low/OK

OK

2004 Hummer H2

2004 ENGINE Engine Cooling - Hummer H2