U1255 Loss of Class II Serial Data Fault

DTC U1255 Loss Of Class II Serial Data Fault:

CIRCUIT DESCRIPTION
The Body Control Module (BCM) receives a vehicle security powertrain status message from the Powertrain Control Module (PCM). If this message is not received within 1 minute of turning the ignition switch to the RUN position, the BCM will set a DTC code and illuminate the vehicle security telltale.

CONDITIONS FOR SETTING THE DTC
^ If this message is not received within one minute of turning ignition switch to the RUN position, the BCM will set a DTC code and illuminate the vehicle security telltale.

ACTION TAKEN WHEN THE DTC SETS
^ Stores a DTC U1255 in the BCM memory.

CONDITIONS FOR CLEARING THE DTC
^ The current code is cleared when the vehicle security powertrain status message is received.
^ A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ Using a scan tool.

DIAGNOSTIC AIDS
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent open in circuit 1132, or 1037.
- Poor connections at the BCM, PCM, or Splice Pack SP205.
- BCM open internally.
^ The BCM may store DTC U1255 if certain diagnostics are performed between the PCM and the Data Link Connector (DLC).
^ DTC P1626 will set in the PCM when the ignition switch is in the RUN position with the BCM disconnected.

TEST DESCRIPTION
Numbers below refer to the step numbers on the diagnostic table
1. Always perform the BCM Diagnostic System Check before attempting to diagnose a DTC U1255.
2. Check if the scan tool tries to communicate with the PCM.
3. Checks if the scan tool tries to communicate with the IPC.
5. Clears all DTC and checks for DTC U1255 again.