Testing the Serial Data Circuit for an Open/High Resistance
- If equipped with a JX 304 splice pack, ignition ON, verify the scan tool communicates with one or more control modules connected to the JX 304 splice pack.
- If all control modules on the JX 304 splice pack do not communicate, test the serial data circuit between the JX 300 and JX 304 splice packs for an open/high resistance. If the circuit tests normal, test each splice pack for an open/high resistance.
- If equipped with a JX 300 splice pack, ignition ON, verify the scan tool communicates with one or more control modules connected to the JX 300 splice pack.
- If all control modules on the JX 300 splice pack do not communicate, test the serial data circuit between the JX 200 and JX 300 splice packs for an open/high resistance. If the circuit tests normal, test the JX 200 splice pack for an open/high resistance.
- Ignition OFF, disconnect one of the harness connectors listed below:
- JX 200 if the control modules not communicating are connected to the JX 200 splice pack
- JX 300 if the control modules not communicating are connected to the JX 300 splice pack
- JX 304 if the control modules not communicating are connected to the JX 304 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.