Testing the Serial Data Circuits for an Open/High Resistance
- Ignition OFF, disconnect the harness connectors with the high voltage energy management high speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
- Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 140 Ω between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are greater than 140 Ω.
- If each pair of serial data circuits is less than the specified range, replace the control module that was disconnected.
- Connect the harness connectors at the control module that was disconnected.
- Disconnect the harness connectors with the high voltage energy management high speed GMLAN serial data circuits at another control module, in the direction of the open circuit.
- Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 140 Ω between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits is greater than 140 Ω.
- If each pair of serial data circuits is less than the specified range, replace the control module that was just disconnected.
- Repeat step 3 until one of the following conditions are isolated:
- An open/high resistance on the serial data circuit between 2 control modules
- An open/high resistance on the serial data circuit between a control module and a terminating resistor
- An open/high resistance terminating resistor