Diagnostic Test

ACTIVE DTC
NOTE: For vehicle communication problems, use the scan tool to refer to the Network Review screen. The screen depicts a high level view of the vehicle network. Fault and problem areas appear in red. Selecting any of the network components allows access to the source of the problem.
1. Ignition on, engine not running.
2. With a scan tool, read DTCs.
  Is the status Active for this DTC?
  
  Yes
  - Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Diagnosis and Testing and perform the U0121-Lost Communication with ABS diagnostic procedure.
  No
  - Refer to Non-DTC Diagnostics/Communication - Diagnosis and Testing and perform the Lost Stored Communication DTC diagnostic procedure.