Testing the Serial Data Circuit for an Open/High Resistance

Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 10 min for all vehicle systems to power down. Disconnect the splice pack containing the devices that are not communicating on the low speed GMLAN serial data circuit.
Test for less than 2 Ω between the X84 Data Link Connector terminal 1 and the disconnected splice pack.
- If 2 Ω or greater
  Repair the open/high resistance in the serial data circuit.
- If less than 2 Ω
Disconnect all devices on the failed serial data circuit.
Test for less than 2 Ω between each section of the failed serial data circuit end to end.
- If 2 Ω or greater
  Repair the open/high resistance in the serial data circuit.
- If less than 2 Ω
Connect the splice pack and connect the first device on the failed serial data circuit.
Verify if the device communicates or not with the scan tool.
- If the device does not communicates
  Repair the open/high resistance in the serial data circuit.
- If the device communicates and there are more devices to connect
  Connect the next device on the failed serial data circuit and repeat step 6.
- If all devices are connected and communicating
All OK.