Testing the Serial Data Circuits for a Short between the Circuits

WARNING: This page is about a different car, the 2011 Chevrolet Volt. However, it is still accessible from the selected car via links, so may be relevant.

Ignition OFF, disconnect the harness connectors with the powertrain high speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
Ignition OFF and all vehicle systems OFF, all key fobs at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 110 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 less than 110 Ω.
- If each pair of serial data circuits is greater 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 powertrain high speed GMLAN serial data circuits at another control module, in the direction of the circuits shorted together.
Ignition OFF and all vehicle systems OFF, all key fobs at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 110 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 less than 110 Ω.
- If each pair of serial data circuits is within the specified range, replace the control module that was just disconnected.
Repeat step 3 until one of the following conditions are isolated:
- Serial data circuits shorted together between 2 control modules
- Serial data circuits shorted together between a control module and a terminating resistor
- A shorted terminating resistor
- Serial data circuits shorted together between the X84B auxiliary data connector and the first control module or splice pack, if equipped