Scan Tool Does Not Communicate with Class 2 Device. Chevrolet TrailBlazer

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2006 🢒 TrailBlazer - 2WD 🢒 Vehicle Control Systems 🢒 Computer/Integrating Systems 🢒 Scan Tool Does Not Communicate with Class 2 Device

Scan Tool Does Not Communicate with Class 2 Device 4.2L w/o Immobilizer

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. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

Diagnostic Aids

•	The body control module (BCM) detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must be connected to the DLC for any other module to communicate with the scan tool.

•	When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set:

U1300

U1301

U1305

Test Description

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

A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on class 2 serial data bus:

•	The body control module (BCM)

•	The communication interface module (OnStar®), w/UE1

•	The digital radio receiver (DRR), w/U2K

•	The driver door module (DDM)

•	The driver seat module (DSM), w/AAB

•	The DVD player

•	The electronic brake control module (EBCM)

•	The endgate module (EGM), for XUV

•	The HVAC control module

•	The HVAC control module - rear auxiliary

•	The inflatable restraint sensing and diagnostic module (SDM)

•	The instrument panel cluster (IPC)

•	The liftgate control module (LGM), except XUV

•	The passenger door module (PDM)

•	The power roof module (PRM), for XUV

•	The powertrain control module (PCM)

•

The radio

•	The transfer case shift control module (TCSCM), w/4WD

The following DTCs may be retrieved with a history status, but are not the cause of the present condition.

A state of health (SOH) DTC with a history status may be present along with a U1000 code having a current status. This indicates that the malfunction occurred when the ignition was ON.

Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.

A poor connection at DLC terminal of the splice pack SP205 would cause this condition but will not set a DTC.

An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module. This condition will not set a DTC.

The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the BCM and the PCM class 2 serial data circuits.

This test isolates the BCM class 2 serial data circuits.

The BCM detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the splice pack SP306 serial data circuits.

This test isolates the rest of the splice pack SP205 serial data circuits.

If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.

The communication malfunction may have prevented diagnosis of the customer complaint.

Step

Action

Yes

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems

Important: This test is used for vehicles with Passlock System, as vehicle theft deterrent.

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Turn ON the ignition, with the engine OFF.
Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature.

Does the scan tool communicate with any module on the class 2 serial data circuit?

Go to Step 3

Go to Step 8

Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
Record all of the displayed DTCs, the DTC status, and the module which set the DTC.

Did you record any DTCs in the range of U1000 to U1305?

Go to Step 4

Go to Step 7

Are the history DTCs U1300, U1301, or U1305 retrieved from any module?

Go to Step 5

Go to Step 6

Important:: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions.

Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems:

•	Testing for Intermittent Conditions and Poor Connections

•	Circuit Testing

•	Connector Repairs

•	Wiring Repairs

Did you find and correct the condition?

Go to Step 25

Go to Step 6

Is U1000 the only DTC displayed in the previously specified range?

Go to DTC U1000

Go to DTC U1001-U1254

Diagnose the non-communicating module by using the DTC U1001-U1254 procedure for the module which is not communicating. Refer to DTC U1001-U1254 .

Did you complete the action?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Turn OFF the ignition.
Disconnect the scan tool from the data link connector (DLC).
Inspect for poor connections at the DLC terminals 2 and 5. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 9

Test the DLC ground circuit at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 10

Disconnect the splice pack SP205.
Inspect for poor connections at the splice pack SP205. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 11

Test the class 2 serial data circuit between the DLC and the splice pack SP205 for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 12

Using the correct terminal adapter, connect a jumper wire to the DLC terminal of the splice pack SP205.
Connect the other end of the jumper wire, using correct terminal adapter, to the body control module (BCM) terminal of the splice pack SP205.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 16

Go to Step 13

Turn OFF the ignition.
Disconnect the powertrain control module (PCM).
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 14

Go to Step 15

Turn OFF the ignition.
Test the class 2 serial data circuit between the splice pack SP205 and the PCM for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 23

Turn OFF the ignition.
Disconnect the BCM.
Test both class 2 serial data circuits of the BCM for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 23

Leave the jumper wire connected to the DLC terminal and to the BCM terminal of the splice pack SP205.
Connect another jumper wire from the jumper wire connected to the DLC terminal of the splice pack SP205.
Connect the other end of the jumper wire, using correct terminal adapter, to the splice pack SP306 terminal of the splice pack SP205.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 21

Go to Step 17

Disconnect the splice pack SP306.
Inspect for poor connections at the splice pack SP306. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 19

Go to Step 18

Repair the class 2 serial data circuit for a short to ground or a short to voltage between the splice pack SP205 and the splice pack SP306. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP306 until the concern is located:

Connect another jumper wire to the splice pack SP205 terminal of the splice pack SP306.
Connect the other end of the jumper wire, using correct terminal adapter, to the terminal for the devices connected to splice pack SP306.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 25

Go to Step 20

Turn OFF the ignition.
Disconnect the module that caused the no communication condition.
Test the class 2 serial data circuit between the splice pack SP306 and the respective module for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 23

Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP205 until the concern is located:

Disconnect the jumper wire from the splice pack SP306 terminal of the splice pack SP205.
Connect the jumper wire, using correct terminal adapter, to the terminal of the rest of modules connected to splice pack SP205.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 25

Go to Step 22

Turn OFF the ignition.
Disconnect the module that caused the no communication condition.
Test the class 2 serial data circuit between the splice pack SP205 and the respective module for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 23

Inspect for poor connections at the class 2 serial data circuit of the module that induced the failure. 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 25

Go to Step 24

Replace the module that induced the failure. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 25

Reconnect all of the disconnected modules.
Reconnect any other disconnected connectors.
Install a scan tool.
Turn ON the ignition, leaving the engine OFF.
Wait for 10 seconds.

The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn OFF the scan tool prior to performing this test.

Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
Record all of the displayed DTCs and the DTC status.

Did you record any DTCs which begin with a "U" and with a current status?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 26

Did you record any DTCs which do not begin with a "U"?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 27

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

Did you complete the action?

System OK

Scan Tool Does Not Communicate with Class 2 Device 4.2L w/Immobilizer

Circuit Description

Diagnostic Aids

•	The body control module (BCM) detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must be connected to the DLC for any other module to communicate with the scan tool.

•	When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set:

U1300

U1301

U1305

Test Description

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

•	The body control module (BCM)

•	The communication interface module (OnStar®), w/UE1

•	The digital radio receiver (DRR), w/U2K

•	The driver door module (DDM)

•	The driver seat module (DSM), w/AAB

•	The DVD player

•	The electronic brake control module (EBCM)

•	The endgate module (EGM), for XUV

•	The HVAC control module

•	The HVAC control module - rear auxiliary

•	The inflatable restraint sensing and diagnostic module (SDM)

•	The instrument panel cluster (IPC)

•	The liftgate control module (LGM), except XUV

•	The passenger door module (PDM)

•	The power roof module (PRM), for XUV

•	The powertrain control module (PCM)

•

The radio

•	The transfer case shift control module (TCSCM), w/4WD

•	The theft deterrent control module (VTD)

The following DTCs may be retrieved with a history status, but are not the cause of the present condition.

A state of health (SOH) DTC with a history status may be present along with a U1000 code having a current status. This indicates that the malfunction occurred when the ignition was ON.

Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.

A poor connection at the DLC terminal of the splice pack SP205 would cause this condition but will not set a DTC.

This step may eliminate the loop created by the PCM and VTD from failure cause.

An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module. This condition will not set a DTC.

This test isolates the PCM class 2 serial data circuits.

This test isolates the rest of the splice pack SP205 serial data circuits.

If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.

The communication malfunction may have prevented diagnosis of the customer complaint.

Step

Action

Yes

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems

Important: This test is used for vehicles with Passkey III+ System (PK3+), as vehicle theft deterrent.

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Turn ON the ignition, with the engine OFF.
Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature.

Does the scan tool communicate with any module on the class 2 serial data circuit?

Go to Step 3

Go to Step 8

Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
Record all of the displayed DTCs, the DTC status, and the module which set the DTC.

Did you record any DTCs in the range of U1000-U1305?

Go to Step 4

Go to Step 7

Are the history DTCs U1300, U1301 or U1305 retrieved from any module?

Go to Step 5

Go to Step 6

Important:: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions.

Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems:

•	Testing for Intermittent Conditions and Poor Connections

•	Circuit Testing

•	Connector Repairs

•	Wiring Repairs

Did you find and correct the condition?

Go to Step 25

Go to Step 6

Is U1000 the only DTC displayed in the previously specified range?

Go to DTC U1000

Go to DTC U1001-U1254

Diagnose the non-communicating module by using the DTC U1001-U1254 procedure for the module which is not communicating. Refer to DTC U1001-U1254 .

Did you complete the action?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Turn OFF the ignition.
Disconnect the scan tool from the data link connector (DLC).
Inspect for poor connections at the DLC terminals 2 and 5. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 9

Test the DLC ground circuit at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 10

Disconnect the splice pack SP205.
Inspect for poor connections at the splice pack SP205. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 11

Using the correct terminal adapter, connect a jumper wire to the DLC terminal of the splice pack SP205.
Connect the other end of the jumper wire, using correct terminal adapter, to the body control module (BCM) terminal of the splice pack SP205.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 18

Go to Step 12

Disconnect the vehicle theft deterrent (VTD).
Test the class 2 serial data circuit between the DLC and the splice pack SP205 for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 13

Using the correct terminal adapter, connect a jumper wire to the DLC terminal of the splice pack SP205.
Connect the other end of the jumper wire, using correct terminal adapter, to the BCM terminal of the splice pack SP205.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 15

Go to Step 14

Turn OFF the ignition.
Disconnect the BCM.
Test the class 2 serial data circuit of the BCM for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 25

Leave the jumper wire connected to the DLC terminal and to the BCM terminal of the splice pack SP205.
Connect another jumper wire from the jumper wire connected to the DLC terminal of the splice pack SP205.
Connect the other end of the jumper wire, using correct terminal adapter, to the powertrain control module (PCM) terminal of the splice pack SP205.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 17

Go to Step 16

Turn OFF the ignition.
Disconnect the PCM.
Test both class 2 serial data circuits of the PCM for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 25

Turn OFF the ignition.
Reconnect the VTD.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 25

Leave the jumper wire connected to the DLC terminal and to the BCM terminal of the splice pack SP205.
Connect another jumper wire from the jumper wire connected to the DLC terminal of the splice pack SP205.
Connect the other end of the jumper wire, using correct terminal adapter, to the splice pack SP306 terminal of the splice pack SP205.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 23

Go to Step 19

Disconnect the splice pack SP306.
Inspect for poor connections at the splice pack SP306. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 21

Go to Step 20

Repair the class 2 serial data circuit between the splice pack SP205 and the splice pack SP306 for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP306 until the concern is located:

Connect another jumper wire to the splice pack SP205 terminal of the splice pack SP306.
Connect the other end of the jumper wire, using correct terminal adapter, to the terminal for the devices connected to splice pack SP306.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 27

Go to Step 22

Turn OFF the ignition.
Disconnect the module that caused the no communication condition.
Test the class 2 serial data circuit between the splice pack SP306 and the respective module for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 25

Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP205 until the concern is located:

Disconnect the jumper wire from the splice pack SP306 terminal of the splice pack SP205.
Connect the jumper wire, using correct terminal adapter, to the terminal of the rest of modules connected to splice pack SP205.
Turn ON the ignition, leaving the engine OFF.
Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 27

Go to Step 24

Turn OFF the ignition.
Disconnect the module that caused the no communication condition.
Test the class 2 serial data circuit between the splice pack SP205 and the respective module for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 25

Did you find and correct the condition?

Go to Step 27

Go to Step 26

Replace the module that induced the failure. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 27

Reconnect all of the disconnected modules.
Reconnect any other disconnected connectors.
Install a scan tool.
Turn ON the ignition, leaving the engine OFF.
Wait for 10 seconds.

The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn OFF the scan tool prior to performing this test.

Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
Record all of the displayed DTCs and the DTC status.

Did you record any DTCs which begin with a "U" and with a current status?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 28

Did you record any DTCs which do not begin with a "U"?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 29

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

Did you complete the action?

System OK

Scan Tool Does Not Communicate with Class 2 Device 5.3L

Circuit Description

Test Description

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

A current DTC, U1300 or U1301, may be retrieved only from the engine control module (ECM), because the ECM is connected to both class 2 and high speed GMLAN buses, but it communicates with the scan tool on high speed GMLAN bus only.

A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The scan tool communicates with the following modules on the class 2 serial data circuit:

•	The body control module (BCM)

•	The communication interface module (OnStar®), w/UE1

•	The digital radio receiver (DRR), w/U2K

•	The driver door module (DDM)

•	The driver seat module (DSM), w/AAB

•	The DVD player

•	The electronic brake control module (EBCM)

•	The endgate module (EGM), for XUV

•	The HVAC control module

•	The HVAC control module - rear auxiliary

•	The inflatable restraint sensing and diagnostic module (SDM)

•	The instrument panel cluster (IPC)

•	The liftgate control module (LGM), except XUV

•	The passenger door module (PDM)

•	The power roof module (PRM), for XUV

•

The radio

•	The transfer case shift control module (TCSCM), w/4WD

•	The theft deterrent control module (VTD), w/BAE

Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.

A poor connection at splice pack SP205 will cause this condition but will not set a DTC.

An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module on the class 2 network. This condition will not set a DTC.

Step	Action	Yes	No
Schematic Reference: Data Link Connector Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Turn ON the ignition, with the engine OFF. Retrieve the DTCs from the engine control module (ECM). Is DTC U1300 or U1301 set?	Go to DTC U1300, U1301, or U1305	Go to Step 3
3	Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature. Does the scan tool communicate with any module on the class 2 serial data circuit?	Go to Step 4	Go to Step 7
4	Did you record any DTCs in the range of U1000-U1255?	Go to Step 5	Go to Step 6
5	Did you record any DTCs in the range of U1001-U1254?	Go to DTC U1001-U1254	Go to DTC U1000
6	Diagnose the non-communicating module by using the DTC U1001-U2154 procedure for the module which is not communicating. Refer to DTC U1001-U1254 . Did you complete the action?	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information	--
7	Turn OFF the ignition. Disconnect the scan tool from the data link connector (DLC). Inspect for poor connections at the DLC terminals 2 and 5. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information	Go to Step 8
8	Test the DLC ground circuit at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information	Go to Step 9
9	Disconnect the splice pack SP205. Inspect for poor connections at the splice pack SP205. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information	Go to Step 10
10	Repair the class 2 serial data circuit between the DLC and the splice pack SP205 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the action?	System OK	--