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Home >> Cadillac >> 2009 >> XLR Base >> Repair and Diagnosis >> Engine Performance >> System >> Data Communication System >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with Class 2 Device >> Circuit/System Testing
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Circuit/System Testing

NOTE: Use the schematic to identify the following:
  • Control modules the vehicle is equipped with
  • Control module locations on the class 2 serial data circuit
  • The class 2 serial data circuit terminals for each control module.
  1. Attempt to communicate with all control modules on the Class 2 serial data circuit, refer to Data Link References . Communications should not be available any control module on the Class 2 serial data circuit.
    • If only one control module is not communicating, diagnose that control module only, refer to DTC U1001-U1254 .
    • If one or more control modules are communicating but not all, refer to Testing the Serial Data Circuit for an Open/High Resistance below.
  2. Disconnect the scan tool from the DLC. The following tests will be done at the DLC connector.
  3. All access doors closed, ignition OFF for 60 seconds, test for less than 10 Ω between the ground circuit terminal 5 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for less than 4.5 V between the serial data circuit terminal 2 and ground.
    • If greater than the specified range, test the serial data circuit for a short to voltage; refer to Testing the Serial Data Circuit for a Short to Voltage below.
  5. Ignition OFF for 60 seconds, test for greater than 100 Ω between the serial data circuit terminal 2 and ground.
    • If less than the specified range, test the serial data circuit for a short to ground; refer to Testing the Serial Data Circuit for a Short to ground below.
  6. Disconnect the harness connector at the JX205 splice pack.
  7. Test for less than 2 Ω between the DLC serial data circuit terminal 2 and the JX205 splice pack terminal A.
    • If greater than the specified range, test the serial data circuit for an open/high resistance. If the circuits test normal, replace the BCM.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors at the JX205 and JX208 splice packs.
  2. Ignition ON, test for less than 4.5 V between the DLC serial data circuit terminal 2 and ground.
    • If greater than the specified range, repair the short to voltage.
  3. Test for less than 4.5 V between each serial data circuit at the splice pack connectors and ground.
    • If greater than the specified range, perform the appropriate test listed below:

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF, disconnect the harness connectors at the JX205 and JX208 splice packs.
  2. Test for infinite resistance between the DLC serial data circuit terminal A and ground.
    • If not the specified value, repair the short to ground.
  3. Ignition OFF for 60 seconds, test for greater than 100 Ω between each serial data circuit at the splice pack connectors and ground.
    • If less than the specified range, perform the appropriate test listed below:

Testing the Serial Data Circuit for an Open/High Resistance

  1. Ignition ON, verify the scan tool communicates with one or more control modules connected to the JX208 splice pack.
    • If all control modules on the JX208 spice pack do not communicate, test the serial data circuit between the JX205 and JX208 splice packs for an open/high resistance. If the circuit tests normal, test each splice pack for an open/high resistance.
  2. Ignition OFF, disconnect one of the harness connectors listed below:
    • JX205 if the control modules not communicating are connected to the JX205 splice pack
    • JX208 if the control modules not communicating are connected to the JX208 splice pack
  3. Install a 3A fused jumper wire between the disconnected splice pack terminal A and a class 2 serial data circuit that is not communicating.
  4. Ignition ON, verify the scan tool communicates with the control modules connected to the class 2 serial data circuit.
    • If any control module does not communicate, test each section of the serial data circuit for an open/high resistance. If the circuits test normal, replace the control module that does not communicate when connected.
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