Hummer H2. Manual - part 236

z

Circuit Testing in Wiring Systems  

z

Wiring Repairs in Wiring Systems  

Did you find and correct the condition?

Go to Step 6

Go to 

Step 2

2

1. Turn OFF the ignition.  

2. Test the ground circuits of the module that is not 

communicating for an open.  

Refer to the following: 

z

Control Module References in Body Control System 
for the applicable Schematic  

z

Circuit Testing in Wiring Systems  

z

Wiring Repairs in Wiring Systems  

Did you find and correct the condition?

Go to Step 6

Go to 

Step 3

3

Test the class 2 serial data circuits of the module that is not 
communicating for an open. Refer to Circuit Testing and 
Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

Go to Step 6

Go to 

Step 4

4

Inspect the harness connectors of the module that is not 
communicating for poor connections and terminal tension at 
the following circuits: 

z

The battery positive voltage input circuits  

z

The battery positive voltage output circuits  

z

The ignition voltage input circuits  

z

The ignition voltage output circuits  

z

The switched battery positive voltage supply circuits  

z

The ground circuits  

z

The class 2 serial data circuits  

 
Refer to the following: 

z

Control Module References in Body Control System 
for the applicable schematic  

z

Testing for Intermittent Conditions and Poor 
Connections in Wiring Systems  

z

Connector Repairs in Wiring Systems  

 

Go to 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Data Link Communications - Hummer H2

  

DTC U1300, U1301, OR U1305 

Circuit Description 

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal 
vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, 
Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 
seconds. When the module detects one of the following conditions on the class 2 serial data circuit for 
approximately 3 seconds, the setting of all other class 2 serial communication DTCs is inhibited and a DTC will 
set. 

DTC U1300, U1301, or U1305 

Did you find and correct the condition?

Go to Step 6

Step 5

5

Replace the module that is not communicating. Refer to 
Control Module References for the applicable replacement 
procedure.Did you complete the replacement?

IMPORTANT:

Perform the programming or set up procedure for the 
module, if required.

Go to Step 6

-

6

1. Install a scan tool.  

2. Turn ON the ignition with the engine OFF.  

3. Select the Display DTCs function for the module 

which was not communicating.  

Does the scan tool display any DTCs which do not begin 
with a "U"?

Go to Control Module 

References for the applicable 

Diagnostic System Check

Go to 

Step 7

7

Select the Display DTCs function for the modules which had 
the Loss of Communications DTC set. 
Does the scan tool display any DTCs which do not begin 
with a "U"?

Go to Control Module 

References for the applicable 

Diagnostic System Check

Go to 

Step 8

8

1. Use the scan tool in order to clear the DTCs.  

2. Continue diagnosing or clearing the DTCs until all the 

modules have been diagnosed and all the DTCs have 
been cleared.  

Did you complete the action?

Go to Control Module 

References for the applicable 

Diagnostic System Check

-

DTC

Condition

U1300 Low voltage on the class 2 serial data circuit.
U1301 High voltage on the class 2 serial data circuit.

U1305

Either high or low voltage on the class 2 serial data circuit. 
Some modules will set DTC U1305 if they are not capable of distinguishing between a short to 
battery voltage or ground.

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Data Link Communications - Hummer H2

  

Conditions for Running the DTCs 

z

Voltage supplied to the module is in the normal operating voltage range.  

z

The vehicle power mode requires serial data communication to occur.  

Conditions for Setting the DTCs 

z

No valid messages are detected on the class 2 serial data circuit.  

z

The voltage level detected on the class 2 serial data circuit is in one of the following conditions: 

{

High  

{

Low  

z

The above conditions are met for approximately 3 seconds.  

Action Taken When the DTCs Sets 

The module uses default values for all parameters received on the class 2 serial data circuit. 

Conditions for Clearing the DTC 

z

A current DTC clears when the malfunction is no longer present.  

z

A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat 
of the malfunction.  

Diagnostic Aids 

z

These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the 
symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to Scan Tool Does Not 
Communicate with Class 2 Device .  

z

An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan 
Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent 
condition. Refer to 

Scan Tool Does Not Communicate with Class 2 Device

 .  

SYMPTOMS - DATA LINK COMMUNICATIONS 

1. Perform the applicable diagnostic system check before using the Symptom Tables in order to verify that 

there are no DTCs set.  

2. Review the system operation in order to familiarize yourself with the system functions. Refer to Data 

Link Communications Description and Operation .  

Visual/Physical Inspection 

z

Inspect for aftermarket devices which could affect the operation of the vehicle systems. Refer to 
Checking Aftermarket Accessories in Wiring Systems. 

IMPORTANT: The following steps must be completed before using the symptom tables.

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Data Link Communications - Hummer H2

  

z

Inspect the easily accessible or visible system components for obvious damage or conditions which could 
cause the symptom.  

Intermittent 

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for 
Intermittent Conditions and Poor Connections in Wiring Systems. 

Symptom List 

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom: 

z

Scan Tool Does Not Power Up  

z

Scan Tool Does Not Communicate with Class 2 Device  

SCAN TOOL DOES NOT POWER UP 

Circuit Description 

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated 
by an industry wide standard, and is required to provide the following: 

z

Scan tool power battery positive voltage at terminal 16  

z

Scan tool power ground at terminal 4  

z

Common signal ground at terminal 5  

The scan tool will power up with the ignition OFF. Some modules however, will not communicate unless the 
ignition is ON and the power mode master (PMM) module sends the appropriate power mode message. 

Test Description 

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

4: If the battery positive voltage and ground circuits of the DLC are functioning properly. The 
malfunction must be due to the scan tool.  

Scan Tool Does Not Power Up 

Step

Action

Yes

No

Schematic Reference: Data Link Connector (DLC) Schematics 
Connector End View Reference: Data Link Communications Connector End Views

1

Test the battery positive voltage circuit of the data link 
connector (DLC) for an open or a short to ground. Refer 
to Circuit Testing or Wiring Repairs in Wiring 
Systems. 
Did you find and correct the condition?

Go to Control Module 

References in Body Control 

System for the applicable 

Diagnostic System Check

Go to 

Step 2

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Data Link Communications - Hummer H2