Testing the Device Circuits

Testing the Device Circuits

1. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between each ground circuit terminal at the device that was just disconnected and ground.
   • If 10 Ω or greater 
   1. Ignition/Vehicle OFF.
   2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
   • If less than 10 Ω 
3. If equipped, verify a test lamp illuminates between each B+ circuit terminal and ground.
   • If the test lamp does not illuminate and the circuit fuse is good 
   1. Ignition/Vehicle OFF, remove the test lamp.
   2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
   • If the test lamp does not illuminate and the circuit fuse is open 
   1. Ignition/Vehicle OFF, remove the test lamp.
   2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the disconnected device.
   • If the test lamp illuminates 
4. Ignition ON/Vehicle In Service Mode.
5. If equipped, verify a test lamp illuminates between each ignition circuit terminal, which has a fuse in the circuit, and ground.
   • If the test lamp does not illuminate and the circuit fuse is good 
   1. Ignition/Vehicle OFF, remove the test lamp.
   2. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse.
   • If the test lamp does not illuminate and the circuit fuse is open 
   1. Ignition/Vehicle OFF, remove the test lamp.
   2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the disconnected device.
   • If the test lamp illuminates 
6. If equipped, verify a test lamp illuminates between each ignition circuit terminal, which is controlled by a control module, and ground.
   • If the test lamp does not illuminate 
   1. Ignition/Vehicle OFF, remove the test lamp, disconnect the harness connectors at the control module that controls the ignition circuit.
   2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
   3. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the control module that controls the ignition circuit.
   • If the test lamp illuminates 
7. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the harness connectors at the K56 Serial Data Gateway Module. It may take up to 2 min for all vehicle systems to power down.
8. Test for less than 2 Ω in each of the gateway expansion high speed GMLAN serial data circuits end to end between the non communicating device and the K56 Serial Data Gateway Module.
   • If 2 Ω or greater 

     Repair the open/high resistance in the serial data circuit.

   • If less than 2 Ω 
9. Test for less than 2 Ω in each of the primary high speed GMLAN serial data circuits (circuit numbers 2500 & 2501) end to end between the K56 Serial Data Gateway Module and the appropriate X84 Data Link Connector (DLC) terminals listed below.
   • X84 Data Link Connector high speed GMLAN serial data circuit terminal 6
   • X84 Data Link Connector high speed GMLAN serial data circuit terminal 14
   • If 2 Ω or greater 

     Repair the open/high resistance in the high speed GMLAN serial data circuit.

   • If less than 2 Ω 
10. Replace the non communicating device that was disconnected.