Circuit/System Verification

Ignition ON/Vehicle In Service Mode.
Verify that no other DTCs are 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
Verify that all high speed GMLAN devices are communicating.
- If only one high speed GMLAN device is not communicating
  Refer to DTC U0100-U02FF to diagnose that device.
- If two or more high speed GMLAN devices are not communicating
  Refer to Scan Tool Does Not Communicate with High Speed GMLAN Device .
- Go to next step: If all high speed GMLAN devices are communicating
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 10 min for all vehicle systems to power down.
Ignition ON/Vehicle In Service Mode.
Clear the DTC.
Verify that the DTC does not reset.
- If the DTC resets
  Replace the K20 Engine Control Module.
- Go to next step: If the DTC does not reset
All OK.