GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2004 🢒 XLR 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Scan Tool Does Not Communicate with Class 2 Device

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 DLC allows communication with the modules for diagnostic purposes.

Test Description

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

  1. A current DTC U1305 may be retrieved only from BCM.

    2.

  2. 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 the class 2 serial data circuit. The BCM is diagnosed only through GMLAN serial data circuit.

    3. • Audio-Amplifier
    • Body Control Module (BCM)
    • CD Changer (CDX)
    • Digital Radio Receiver (DRR)
    • Driver Door Module (DDM)
    • Driver Door Switch (DDS)
    • Driver Position Module (DPM)
    • Fold Top Controller (FTC)
    • Head Up Display (HUD)
    • HVAC Control Module
    • Inflatable Restraint Sensing and Diagnostic Module (SDM)
    • Instrument Panel Cluster (IPC)
    • Passenger Door Module (PDM)
    • Radio
    • Remote Control Door Lock Receiver (RCDLR)
    • Steering Column Lock Control Module (SCLCM)
    • Vehicle Communication Interface Module (VCIM)

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

    4.

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

    5.

  5. 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

  1. Turn ON the ignition, with the engine OFF.
  2. Perform the Vehicle DTC Information function on the scan tool under Computer/Integrating Systems menu.

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

Go to DTC U1300, U1301, or U1305

Go to Step 3

3

Did 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 to U1255?

Go to Step 5

Go to Step 6

5

Did you record any DTCs in the range of U1001 to U1254?

Go to DTC U1001-U1254

Go to DTC U1000 and U1255

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

  1. Turn OFF the ignition.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. 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

  1. Disconnect the splice pack SP205.
  2. 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

--