Testing the Serial Data Circuit for an Open/High Resistance
- If equipped with a JX 405 splice pack, ignition ON, verify the scan tool communicates with one or more control modules connected to the JX 405 splice pack.
- If all control modules on the JX 405 spice pack do not communicate, test the serial data circuit between the JX 205 and JX 405 splice packs for an open/high resistance. If the circuit tests normal, test each splice pack for an open/high resistance.
- Ignition OFF, disconnect one of the harness connectors listed below:
- JX 205 if the control modules not communicating are connected to the JX 205 splice pack
- JX 405 if the control modules not communicating are connected to the JX 405 splice pack
- Install a 3A fused jumper wire between the disconnected splice pack terminal 1 and a low speed GMLAN serial data circuit that is not communicating.
- Ignition ON, verify the scan tool communicates with the control modules connected to the low speed GMLAN serial data circuit.
- If any control module does not communicate, test each section of the serial data circuit for an open/high resistance. If the circuits test normal, replace the control module that does not communicate when connected.