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Home >> Chevrolet >> 2006 >> SSR Standard >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Computer/Integrating Systems >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with Class 2 Device >> Test Description

Test Description

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

  1. 3:  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 engine control module (ECM) and the transmission control module (TCM) communicate functionally on both high speed GMLAN and class 2 serial data circuits. The ECM and TCM communicate with the scan tool on high speed GMLAN only. The auxiliary gage center, w/ERG or ERH, is on class 2 serial data bus but doesn't have diagnostic capability. The following modules communicate with the scan tool on the class 2 serial data circuit:
    • The audio amplifier (AMP), w/Bose
    • The body control module (BCM)
    • The electronic brake control module (EBCM)
    • The inflatable restraint sensing and diagnostic module (SDM)
    • The instrument panel cluster (IPC)
    • The memory seat module (MSM) - driver, w/AAB
    • The radio
    • The remote control door lock receiver (RCDLR)
    • The roof/door module (RDM)
  2. 4:  The following DTCs may be retrieved with a history status, but are not the cause of the present condition.
    • U1300
    • U1301
    • U1305
  3. 7:  A state of health DTC with a history status may be present along with a U1000 or U1255 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
  4. 8:  Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
  5. 11:  A poor connection at the DLC terminal of the splice pack SP201 would cause this condition but will not set a DTC.
  6. 12:  An open or a short in the class 2 serial data circuit between the DLC and splice pack SP201 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
Scan Tool Does Not Communicate with Class 2 Device

Step Action Yes No
Schematic Reference: Data Link Connector (DLC) 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 Retrieve DTCs from the engine control module (ECM).
Did you record DTCs U1300 or U1301?		 Go to DTC U1300, U1301, or U1305  Go to Step 3 
3 
  1. Turn ON the ignition, leaving the engine OFF.
  2. 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 9 
4 
  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 do 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 5  Go to Step 8 
5 Are the history DTCs U1300, U1301, or U1305 retrieved from any module? Go to Step 6  Go to Step 7 
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:Did you find and correct the condition?		 Go to Diagnostic System Check - Vehicle in Vehicle DTC Information -
7  Are U1000 or U1255 the only DTCs displayed in the previously specified range? Go to DTC U1000 and U1255  Go to DTC U1001-U1254 
8  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 -
9
  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 10 
10 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 11 
11 
  1. Disconnect the splice pack SP201.
  2. Inspect for poor connections at the splice pack SP201. 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 12 
12  Repair the class 2 serial data circuit between the splice pack SP201 and DLC for an open. Refer to Circuit Testing andWiring Repairs in Wiring Systems.
Did you complete the repair?		 System OK -
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