Circuit/System Verification

Ignition ON/Vehicle In Service Mode.
Verify that DTC U0073, U0074, U0075, U0077, U0078, U007A, P06E4, P1EB9, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1428, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set.
- If any of the DTCs are set
  Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Go to next step: If none of the DTCs are set
Attempt to communicate with all devices on the gateway isolated high speed GMLAN serial data circuits. Refer to Data Link References to determine which devices are on the gateway isolated high speed GMLAN bus.
Verify which devices are communicating on the gateway isolated high speed GMLAN serial data circuits.
- If only one device is not communicating
  Refer to Testing the Device Circuits .
- If one or more devices are communicating but not all, except the K56 Serial Data Gateway Module
  Refer to Testing the Serial Data Circuits for an Open/High Resistance .
- Go to next step: If none of the devices are communicating, except the K56 Serial Data Gateway Module
Refer to Circuit/System Testing .