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 low speed GMLAN serial data circuit. Refer to Data Link References to determine which devices are on the gateway isolated low speed GMLAN bus.
Verify that all gateway isolated low speed GMLAN devices are communicating.
- If only one device is not communicating
  Refer to Testing the Device Circuits .
- If all devices are not communicating, except the K56 Serial Data Gateway Module
  Refer to Circuit/System Testing .
- If two or more devices are not 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 all devices are communicating
All OK.