Circuit/System Testing

Low Speed GMLAN Initial Test 

1. Test for less than 1 ohm of resistance between the DLC ground circuit terminal 5 and ground.
   • If greater than the specified range, test the ground circuit for open/high resistance.
2. Ignition OFF, disconnect the harness connector (splice pack comb) at JX205. Test for infinite resistance between the following JX205 serial data circuit terminals and ground.
   • Terminal A
   • Terminal B
   • If less than the specified value, test the serial data circuit for a short to ground.
3. Test for less than 0.1 volt between the following JX205 serial data circuit terminals and ground.
   • Terminal A
   • Terminal B
   • If greater than the specified range, test the serial data circuit for a short to voltage.
4. Test for less than 1 ohm of resistance on the serial data circuit between terminal A of JX205 and terminal 1 of the DLC.
   • If greater than the specified range, test the serial data circuit for open/high resistance.
5. Ignition OFF, install a 3-amp fused jumper wire between terminal A and terminal F of JX205. Attempt to communicate with the inflatable restraint sensing and diagnostic module (SDM). Communication should be available.
   • If no communication is established, refer to SDM Serial Data Circuit Test.
IMPORTANT: After each connection, cycle the ignition key off for 5 seconds, then ON before attempting to establish communication.
6. Ignition OFF, with the jumper wire still attached to terminal A, 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 D, radio
   • Terminal G, instrument panel cluster (IPC)
   • Terminal H, remote control door lock receiver (RCDLR)
   • Terminal K, TDM
   • Terminal L, HVAC control module
   • Terminal M, BCM
   • If any module does not communicate, test the serial data circuit between the applicable module harness connector and the JX205 harness connector for a short to ground or a short to voltage. If the circuit tests normal, replace the applicable module.

SDM Serial Data Circuit Test 

IMPORTANT: Ensure a 3-amp fused jumper wire is installed between terminal A and terminal F of JX205.
1. Ignition OFF, disconnect the harness connector of the inflatable restraint passenger presence system (PPS) module. Attempt to communicate with the SDM. Communication should not be available.
   • If communication is established, replace the PPS module.
2. Ignition OFF, disconnect harness connector X3 at the heated seat control module if equipped (KA1). Attempt to communicate with the SDM. Communication should not be available.
   • If communication is established, replace the heated seat control module.
3. Ignition OFF, disconnect harness connector X1 at the vehicle communication interface module (VCIM) if equipped (UE1). Attempt to communicate with the SDM. Communication should not be available.
   • If communication is established, replace the VCIM.
4. Ignition OFF, disconnect the harness connector at the Digital radio receiver (DRR) if equipped (U2K). Attempt to communicate with the SDM. Communication should not be available.
   • If communication is established, replace the DRR.
5. Ignition OFF, disconnect the harness connector at the SDM. Test for infinite resistance between the following SDM serial data circuit terminals and ground.
   • Terminal 2
   • Terminal 3
   • If less than the specified value, test the serial data circuit for a short to ground.
6. Ignition ON, test for less than 0.1 volt between the following SDM serial data circuit terminals and ground.
   • Terminal 2
   • Terminal 3
   • If greater than the specified range, test the serial data circuit for a short to voltage.
7. If the circuits test normal, replace the SDM.