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HOMESERVICE MANUALSCHEVROLET2019EXPRESS 2500 BASE, VAN CARGO EXTENDED, 6.0L ENG VIN GREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 24 (DATA COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH LOW SPEED GMLAN DEVICECIRCUIT/SYSTEM TESTING
2019 Chevrolet Express 2500 Base, Van Cargo Extended, 6.0L Eng VIN G

Circuit/System Testing

2019 Chevrolet Express 2500 Base, Van Cargo Extended, 6.0L Eng VIN GSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2018 GMC Savana 3500, 2018 GMC Savana 2500, 2018 Chevrolet Express 3500, and 2018 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

Use the schematic to identify the following:

  • Control modules the vehicle is equipped with
  • Control module locations on the low speed GMLAN serial data circuit
  • The low speed GMLAN serial data circuit terminals for each control module
  1. Attempt to communicate with all control modules on the low speed GMLAN serial data circuit. Refer to Data Link ReferencesΒ . Communications should not be available with two or more control modules on the low speed GMLAN serial data circuit.
    • If only one control module is not communicating, diagnose that control module only. Refer to DTC U0100-U02FFΒ .
    • If one or more control modules are communicating but not all, refer to Testing the Serial Data Circuit for an Open/High Resistance.
  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 Ξ© 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 1 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.
  5. Ignition OFF for 60 seconds, test for greater than 100 Ξ© between the serial data circuit terminal 1 and ground.
    • If less than the specified range, test the serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to ground.
  6. Disconnect the appropriate harness connector at the JX 200 splice pack.
  7. Test for less than 2 Ξ© between the DLC serial data circuit terminal 1 and the JX200 splice pack terminal 1.
    • If greater than the specified range, test the serial data circuit for an open/high resistance. If the circuits test normal, replace the splice pack.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the appropriate harness connectors at the JX 200 splice pack.
  2. Ignition ON, test for less than 4.5 V between the DLC serial data circuit terminal 1 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 connector and ground.
    • If greater than the specified range, perform the appropriate test listed below:
    • Serial data circuits with one control module, test the serial data circuit for a short to voltage. If the circuit tests normal replace the control module.
    • Serial data circuits with 2 or more control modules, test each section of the serial data circuit for a short to voltage. If the circuits test normal, replace the control module that causes the short to voltage when connected.

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF, disconnect the appropriate harness connectors at the JX 200 splice pack.
  2. Test for infinite resistance between the DLC serial data circuit terminal 1 and ground.
    • If not the specified value, repair the short to ground.
  3. Ignition OFF for 60 seconds, test for greater than 100 Ξ© between each serial data circuit at the splice pack and ground.
    • If less than the specified range, perform the appropriate test listed below:
    • Serial data circuits with one control module, test the serial data circuit for a short to ground. If the circuit tests normal replace the control module.
    • Serial data circuits with 2 or more control modules, test each section of the serial data circuit for a short to voltage. If the circuits test normal, replace the control module that causes the short to ground when connected.

Testing the Serial Data Circuit for an Open/High Resistance

  1. Ignition OFF, disconnect the appropriate harness connectors at the JX 200 splice pack.
  2. Install a 3 A fused jumper wire between the disconnected splice pack connector terminal 1 and a low speed GMLAN serial data circuit terminal that is not communicating.
  3. Ignition ON, verify the scan tool communicates with the control modules connected to the low speed GMLAN 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.
  4. If all circuits test normal, replace the splice pack.
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