Circuit/System Verification

Ignition ON/Vehicle In Service Mode.
Verify that DTC U0073, U0074, U0075, U0077, U0078, U007A, U007B, U007C, U007D, U1814, U2099, U2100, B1325, B1330, B1370, B1380, B1424, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, P0562, P06E4, or P1EB9 is not set.
- If any of the DTCs are set
  Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- If none of the DTCs are set
Verify that the K56 Serial Data Gateway Module is communicating.
- If the K56 Serial Data Gateway Module is not communicating
  Refer to Circuit/System Testing to diagnose the K56 Serial Data Gateway Module first.
- If the K56 Serial Data Gateway Module is communicating
Determine the device that is not communicating. Refer to Control Module U Code List .
Refer to Data Link References to determine which data communication bus the non communicating device is on.
- If the device is on Gateway Expansion High Speed GMLAN bus
  Refer to Scan Tool Does Not Communicate with Gateway Expansion High Speed GMLAN Device to diagnose that device.
- If the device is on Gateway Isolated High Speed GMLAN bus
  Refer to Scan Tool Does Not Communicate with Gateway Isolated High Speed GMLAN Device to diagnose that device.
- If the device is on Gateway Isolated Low Speed GMLAN bus
  Refer to Scan Tool Does Not Communicate with Gateway Isolated Low Speed GMLAN Device to diagnose that device.
- If the device is not on Gateway Expansion High Speed GMLAN bus, Gateway Isolated High Speed GMLAN bus, and Gateway Isolated Low Speed GMLAN bus
Refer to Circuit/System Testing.