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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Savana 🢒 Body and Accessories 🢒 Theft Deterrent 🢒 Scan Tool Does Not Communicate with Class 2 Device

Circuit Description

Modules connected to the class 2 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. 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
    • When the class 2 circuit is shorted to ground, U1300 will be set. Refer to DTC U1300 .
    • When the class 2 circuit is shorted to battery positive voltage, U1301 will be set. Refer to DTC U1301 .

Test Description

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

    • Electronic brake control module (EBCM)
    • Powertrain control module (PCM)
    • Radio (IRC)
    • Vehicle theft deterrent (VTD)
    • Vehicle immobilizer module (VIM)
    • Inflatable restraint sensing and diagnostic module (SDM)

  1. The following DTCs may be retrieved with a history status:

    • U1300
    • U1301

These DTCs are not the cause of the present condition.

  1. A State of Health DTC with a history status may be present along with a U1000 or U1255 having a current status. This indicates that the malfunction occurred when the ignition was ON.

  1. DLC terminals 2 and 5 provide the connection to the class 2 circuit and the signal ground circuit.

  1. Poor continuity at S207 and/or S153 would cause this condition but will not set a DTC.

  1. An open in the class 2 circuit between the DLC and S207 will prevent the scan tool from communicating with any module. This condition will not set a DTC.

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

  1. This test isolates the PCM class 2 circuit.

  1. This test isolates the VTD/VIM class 2 circuit.

  1. This test isolates the EBCM class 2 circuit.

  1. This test isolates the SDM class 2 circuit.

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

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

1

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up

2

  1. Turn ON the ignition leaving the engine OFF.
  2. Attempt to communicate with each module on the class 2 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 circuit?

Go to Step 3

Go to Step 7

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 models have DTCs set.
  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 Diagnostic Aids

4

Are the 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 23

Go to Step 6

6

Is U1000 or U1255 the only DTC displayed in the previously specified range?

Go to DTC U1000 and U1255

Go to DTC U1001-U1254

7

  1. Turn OFF the ignition.
  2. Remove the scan tool from the 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 Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 8

8

Test the DLC signal ground circuit for an open. Refer to Circuit Testing and 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 9

9

Inspect for poor continuity at S207 and S153. 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 S207.
  2. Test the class 2 circuit for an open or a short between the DLC and S207. Refer to Circuit Testing and 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 11

11

  1. Connect a jumper wire to the end of the DLC class 2 circuit.
  2. Connect the other end of the jumper wire to the end of the IRC class 2 circuit.
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with the IRC.

Does the scan tool communicate with the IRC?

Go to Step 13

Go to Step 12

12
  1. Turn OFF the ignition.
  2. Remove the IRC connector.
  3. Test the IRC class 2 circuit for a short to ground or a short to battery positive voltage. Turn ON the ignition leaving the engine OFF when testing for a short to positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

Go to Step 21

13

  1. Remove the jumper wire from the IRC.
  2. Connect the jumper wire to the following pin on the PCM, depending on engine RPO:
    3. • L18/L35 pin 58, C1
    • L30/31 pin 59, C1
    • L65 pin C8, C3
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with the PCM.

Does the scan tool communicate with the PCM?

Go to Step 15

Go to Step 14

14
  1. Turn OFF the ignition.
  2. Remove the connector from the PCM that contains the class 2 circuit.
  3. Test the class 2 circuit for a short to ground or short to battery positive voltage. Turn ON the ignition leaving the engine OFF when testing for a short to positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 23

Go to Step 21

15

  1. Remove the jumper wire from the PCM.
  2. Connect the jumper wire to the end of the following theft class 2 circuit, depending on theft content:
    3. • Domestic VTD pin B4
    • Export VIM Use two jumper wires for pins C and D of the VIM
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with the VTD/VIM.

Does the scan tool communicate with the VTD/VIM?

Go to Step 17

Go to Step 16

16
  1. Turn OFF the ignition.
  2. Remove the VTD/VIM connector.
  3. Test the VTD/VIM class 2 circuit/circuits for a short to ground or a short to battery positive voltage. Turn ON the ignition leaving the engine OFF when testing for a short to positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 23

Go to Step 21

17
  1. Remove the jumper wire/wires from the VTD/VIM.
  2. Connect a jumper wire to the end of the EBCM class 2 circuit.
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with the EBCM.
  5. For 5.0, 5.7, and 8.1 engines, test for continuity between pins 58 and 59 of C1. If continuity does not exist replace PCM. Refer to Control Module References in Body Control Systems for the correct PCM replacement procedure.

Does the scan tool communicate with the EBCM?

Go to Step 19

Go to Step 18

18
  1. Turn OFF the ignition.
  2. Remove the connector that contains the EBCM class 2 circuit.
  3. Test the EBCM class 2 circuit for a short to ground or a short to battery positive voltage. Turn ON the ignition leaving the engine OFF when testing for a short to positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 23

Go to Step 21

19

  1. Remove the jumper wire from the EBCM.
  2. Connect the jumper wire to the end of the SDM class 2 circuit.
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with the SDM.

Does the scan tool communicate with the SDM?

Go to Step 21

Go to Step 20

20
  1. Turn OFF the ignition.
  2. Remove the SDM connector.
  3. Test the SDM class 2 circuit for a short to ground or a short to battery positive 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 23

Go to Step 21

21

Inspect for poor connections at the class 2 circuit of the module that is not communicating. 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 23

Go to Step 22

22

Replace the module which is not communicating. Refer to Control Module References in Body Control System for the appropriate Repair Instructions.

Did you complete the replacement?

Go to Step 23

--

23
  1. Connect all of the modules.
  2. Connect any other connectors.
  3. Connect a scan tool.
  4. Turn ON the ignition leaving the engine OFF.
  5. 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. Remove the scan tool prior to performing this test.
  6. 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.
  7. 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 Step 25

Go to Step 24

24

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

Go to Step 25

Go to Step 27

25

Diagnose the DTCs as directed by the diagnostic procedures for the particular module or malfunction. Refer to Control Module References in Body Control System for the applicable Diagnostic System Check.

Did you complete the action?

Go to Step 26

--

26

Did you diagnose all of the DTCs?

Go to Step 27

Go to Step 25

27

Use the scan tool in order to clear the DTCs.

Did you complete the action?

System OK