Testing the Serial Data Circuits for an Open/High Resistance
WARNING: This page is about a different car, the 2011 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the harness connectors with the high speed GMLAN serial data circuits at an easily accessible control module that is not communicating and has 2 or more pairs of serial data circuits or an internal terminating resistor.
- 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 speed GMLAN serial data circuits at another control module which has 2 or more pairs of serial data circuits or an internal terminating resistor, 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 are 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 or splice packs, if equipped
- An open/high resistance on the serial data circuit between a control module and a terminating resistor
- An open/high resistance terminating resistor
NOTE:
A control module that has only one pair of high speed GMLAN serial data circuits and no internal terminating resistor should not be disconnected during this diagnostic test. A control module with a single pair of serial data circuits and no internal terminating resistor that has an open/high resistance would be diagnosed in the single control module not communicating diagnostic.
The serial data circuits directly between a control module and the DLC do not need to be tested.
The serial data circuits directly between a control module and the DLC do not need to be tested.