Circuit/System Testing

Low Speed GMLAN Initial Test

1. Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground.
   • If greater than 1.0 ohm, test the ground circuit for open/high resistance.
2. Ignition OFF, disconnect the harness connector (splice pack comb) at JX209.
3. Ignition ON, with a scan tool, attempt to communicate with the BCM.
   • If communication is available, refer to Diagnostic 2.
   • If communication is not available refer to Diagnostic 1.

Diagnostic 1

1. Ignition OFF, disconnect the harness connector (splice pack comb) at JX200.
2. Ignition OFF, disconnect the harness connector at the inflatable restraint passenger presence system (PPS) sensor.
3. Ignition ON, with a scan tool, attempt to communicate with the (BCM). Communication should be available.
   • If no communication, test the serial data circuit between the DLC, BCM, and the PPS sensor for a short to ground and short to voltage. If the circuit tests normal, replace the BCM.
4. Ignition OFF, connect the harness connector at the PPS sensor.
5. Ignition ON, attempt to communicate with the BCM. Communication should be available.
   • If no communication, replace the PPS sensor.
6. Ignition OFF, install a 3-amp fused jumper wire to terminal H of JX200 harness side and terminal G.
7. Ignition ON, attempt to communicate with the IPC. Communications should be available.
   • If communication is not available, test the serial data circuit between the splice pack terminal H and the IPC for a short to ground or a short to voltage. If the circuit tests normal, replace the IPC.
IMPORTANT: After each connection, cycle the ignition key off for 5 seconds, then ON before attempting to establish communication.
8. Ignition OFF, with the jumper wire still attached to terminal H, individually move the other end of the jumper wire to each of the terminals listed below and attempt to communicate with the applicable module. Communications should be available with each module listed.
   • Terminal G, instrument panel cluster (IPC)
   • Terminal J, radio
   • Terminal E, TDM
   • Terminal C, HVAC control module
   • Terminal D, remote control door lock receiver (RCDLR)

• If any module does not communicate, test the serial data circuit between the applicable module harness connector and the JX200 harness connector for a short to ground or a short to voltage. If the circuit tests normal, replace the applicable module.

Diagnostic 2

1. Ignition OFF, disconnect the harness connector (splice pack comb) at JX200.
2. Ignition OFF, install a 3-amp fused jumper wire to terminal H of JX200 harness side and terminal C of JX209 splice pack harness side.
3. Ignition ON, attempt to communicate with the inflatable restraint vehicle roll over sensor. Communication should be available.
   • If communication is not available, test the serial data circuit between the JX209 splice pack terminal C and the inflatable restraint vehicle roll over sensor for a short to ground or a short to voltage. If the circuit tests normal, replace the inflatable restraint vehicle roll over sensor.
IMPORTANT: After each connection, cycle the ignition key off for 5 seconds, then ON before attempting to establish communication.
4. Ignition OFF, with the jumper wire still attached to terminal H, individually move the other end of the jumper wire to each of the terminals listed below and attempt to communicate with the applicable module. Communications should be available with each module listed.
   • JX209 terminal F, rear seat audio
   • JX209 terminal B, inflatable restraint sensing and diagnostic module (SDM)
   • JX209 terminal D, digital radio receiver
   • JX209 terminal E, vehicle control interface module (VCIM)

• If any module does not communicate, test the serial data circuit between the applicable module harness connector and the JX209 harness connector for a short to ground or a short to voltage. If the circuit tests normal, replace the applicable module.