U1255 General Loss of Serial Data Communication - HVAC

CIRCUIT DESCRIPTION
This DTC refers to a generic loss of serial data with an unknown module. This code generally will set when the vehicle is first started, and the Air Conditioning Programmer (ACM) or Climate Control Panel (CCP) requests information from another module and does not get a response. This DTC will clear when the module with the information that the ACM or CCP is requesting comes back "On-Line."

TEST CONDITION(S)
1. Ignition in ON.

FAILURE CONDITION(S)
1. Open circuit.

ACTION TAKEN
1. Set DTC U1255

TROUBLESHOOTING HINTS
If DTC U1255 is set each ignition cycle even through the code was cleared, the following items should be checked.
1. Check DTCs for the Instrument Panel Cluster (IPC), Body Control Module (PZM) and PCM. If the IPC has set code DTC U1152 or if the PCM has set P1605 then replace the ACM. If the IPC, PCM or PZM has set code DTC U1153 the replace the CCP.
2. Check the option bytes in the IPC. Make sure that the correct options have been programmed into the IPC.
3. Check that the proper ACM has been installed in the vehicle.

^ If all of the three checks above are OK, the ACM and CCP is OK, do not replace the components.