U1255 Serial Data Line Malfunction

DTC U1255 Serial Data Line Malfunction:

DTC U1255 Serial Data Line Malfunction:

CIRCUIT DESCRIPTION
The BCM receives a vehicle security Powertrain status message from the PCM through the Class II serial data link when turning the ignition switch on.

CONDITIONS FOR SETTING THE DTC
The BCM sets DTC U1255 when the BCM does not receive a vehicle security Powertrain status message from the PCM within one minute of turning ignition switch on.

ACTION TAKEN WHEN THE DTC SETS
^ The BCM stores DTC U1255 in memory.
^ The SERVICE VEHICLE SOON indicator lamp turns on.
^ The BCM sends a message to the instrument cluster to turn on the SECURITY indicator lamp through the Class II serial data link.

CONDITIONS FOR CLEARING THE DTC
^ DTC1 255 status changes from current to history when the BCM receives the vehicle security powertrain status message from the PCM.
^ A history DTC will clear after 100 consecutive ignition cycles if the condition for the fault 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 1049 or 1037.
- Poor connections at the BCM PCM, or Splice Pack SP205.
- The BCM is 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 on with the BCM disconnected.

TEST DESCRIPTION
The number below refers to the step number on the diagnostic table.
3. This step determines whether the malfunction is intermittent or the BCM is faulty.