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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 SSR 🢒 Preface 🢒 Cautions and Notices 🢒 Scan Tool Does Not Communicate with Class 2 Device

Circuit Description

Each module connected to the class 2 serial data circuit monitors 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.

Diagnostic Aids
    • 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.
    • The body control module (BCM) must be connected to the class 2 serial data circuit for any other module to communicate with the scan tool. The BCM detects that the ignition is ON and sends the appropriate power mode message to wake up the other modules.
    • When the class 2 serial data circuit is shorted to ground or voltage, the following DTCs may set:
      • U1300
      • U1301
      • U1305

Test Description

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

  1. A partial loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.

    2.

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

    3. • U1300
    • U1301
    • U1305

  3. Use the DTC U1000 or U1255 diagnostic procedure if there is communication with some but not all modules, and no DTCs are set.

    4.

  4. Normal class 2 serial data communication cannot take place until the BCM sends the appropriate power mode message. If the BCM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.

    5.

  5. The circuit and module that you jumpered to the DLC class 2 serial data circuit when you lost communication with the BCM is suspect.

    6.

  6. The communication concern may have prevented diagnosis of the customer complaint.

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

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

1

Install a scan tool.

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up

2

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate with each module on the class 2 serial data circuit.

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

Go to Step 3

Go to Step 8

3
  1. 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 have set DTCs.
  2. 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

4

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

Go to Step 5

Go to Step 6

5

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:

    •  Circuit Testing
    •  Connector Repairs
    •  Wiring Repairs

Did you find and correct the condition?

Go to Step 16

Go to Step 6

6

Are any DTCs U1001-U1254 stored as current or history DTCs in any module?

Go to DTC U1001-U1254

Go to DTC U1000 and U1255

7

Diagnose the non communicating module by using the DTC U1001--U1254 Lost Communications with XXX procedure for the module which is not communicating. The DTC U1001--U1254 Lost Communications with XXX procedure will determine which module is not communicating. Refer to DTC U1001-U1254 .

Did you complete the action?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

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8

  1. Turn OFF the ignition.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections and terminal tension at the DLC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector 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 9

9

Test the signal ground circuits of the DLC for an open or high resistance. Refer to Testing for Intermittent Conditions and Poor Connections and Connector 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 10

10

  1. Remove the class 2 serial data splice pack comb.
  2. Connect a jumper between the DLC class 2 serial data circuit and the body control module (BCM) class 2 serial data circuit terminals of the splice pack.
  3. Connect the scan tool.
  4. Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 14

Go to Step 11

11
  1. Disconnect the powertrain control module (PCM).
  2. Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 15

Go to Step 12

12

  1. Disconnect the remote control door lock receiver (RCDLR).
  2. Attempt to communicate with the BCM.

Does the scan tool communicate with the BCM?

Go to Step 15

Go to Step 13

13

  1. Test the following circuits for an open, short to ground, or a short to voltage:
    2. • DLC class 2 serial data circuit between the DLC and the splice pack
    • The DLC class 2 serial data circuit between the splice pack and the RCDLR
    • BCM class 2 serial data circuit
    • The class 2 serial data circuit between the BCM and PCM
  2. Test the following circuits of the BCM for an open or high resistance:
    3. • The battery positive voltage input circuits
    • The battery positive voltage output circuits
    • The ignition voltage input circuits
    • The ignition voltage output circuits
    • The switched battery positive voltage supply circuits
    • The ground circuits

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 16

14

Important: Leave the jumper connected between the BCM and DLC in the splice pack. The BCM must remain connected to the DLC in order to communicate.

Using a 3A fused jumper wire at the splice pack, perform the following in order to determine which class 2 serial data circuit or module is causing the concern:

  1. Turn ON the ignition, with the engine OFF.
  2. Communicate with the BCM using the scan tool.
  3. Jumper one module at a time to the DLC class 2 serial data circuit at the splice pack until communication with the BCM is lost.

Did you complete the action?

Go to Step 15

--

15

Test the class 2 serial data circuits to the suspect module for a short to ground or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 16

16

Inspect for poor connections and terminal tension at the harness connector of the suspect module. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 17

17

Important:  Perform the module programming or setup procedure if required.

Replace the suspect module. Refer to Control Module References in Body Control System for the appropriate Repair Instructions for module replacement.

Did you complete the replacement?

Go to Step 18

--

18

  1. Connect all of the modules.
  2. Connect all of the connectors.
  3. Turn ON the ignition leaving the engine OFF.

    4. Important: 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 or disconnect the scan tool before you display DTCs.

  4. Wait for 10 seconds.
  5. 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 have set DTCs.
  6. Record all of the displayed DTCs and the DTC status.

Did your record any current DTCs?

Go to Step 19

Go to Step 20

19

Diagnose the DTCs as directed by the diagnostic procedures for the particular module or concern.

Did you complete the action?

Go to Step 20

--

20

Clear all DTCs with the scan tool.

Did you complete the action?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

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