B1255

DTC B1255 Generic Loss Of Communications:

CIRCUIT DESCRIPTION
The heater-A/C control communicates with other vehicle Systems, such as the Powertrain Control Module (PCM), through the Class II serial data link. The heater-A/C control uses the Class II serial data link to request the PCM to enable the A/C compressor clutch during A/C operation.

CONDITIONS FOR SETTING THE DTC
The heater-A/C control sets DTC U1255 when the heater-A/C control does not receive data from the Class II serial data link.

ACTION TAKEN WHEN THE DTC SETS
The heater-A/C control stores DTC U1255 in memory.

CONDITIONS FOR CLEARING THE DTC
^ DTC U1255 status changes from current to history when the heater-A/C control receives data from the Class II serial data link.
^ A history DTC will clear after 100 consecutive drive cycles it 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 1132 (PPL) circuit 1049 (DK GRN) or, circuit 1038 (WHT)
- Poor connections at the heater-A/C control, PCM, or Splice Pack SP205
- The heater-A/C control is open internally.
^ The heater-A/C control may store DTC U1255 if certain diagnostics are performed between the Powertrain Control Module (PCM) and the Data Link Connector (DLC).

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 heater-A/C control is faulty.