Testing the Serial Data Circuits 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 harness connectors with the chassis high speed GMLAN serial data circuits at an easily accessible device that is not communicating.
Test for less than 130 Ω between each pair of serial data circuits at the device connector that was just disconnected.
- If each pair of serial data circuit is 130 Ω or less
  Replace the device that was disconnected.
- If any pair of serial data circuits is greater than 130 Ω
Connect the harness connectors at the device that was disconnected.
Disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at another device, in the direction of the circuit with the open/high resistance.
Test for less than 130 Ω between each pair of serial data circuits at the device connector that was just disconnected.
- If each pair of serial data circuits is 130 Ω or less
  Replace the device that was disconnected.
- If any pair of serial data circuits is greater than 130 Ω
Repeat step 3 until one of the following conditions are isolated:
- An open/high resistance on the serial data circuit between two devices or splice packs, if equipped.
- An open/high resistance on the serial data circuit between a device and a terminating resistor.
- An open/high resistance terminating resistor.