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 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 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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Data Link Connector system check performed? | -- | Go to Data Link Connector Schematics in Data Link Communications | |
2 | Was the heater-A/C control diagnostic system check performed? | -- | Go to Diagnostic System Check | |
Does DTC U1255 reset as a current DTC in the heater-A/C control? | -- | |||
4 | Replace the heater-A/C control. Refer to Control Assembly Replacement . Is the repair complete? | -- | -- | |
5 | The malfunction is not present at this time. Refer to Scan Tool Diagnostics for additional information regarding this DTC. Is the action complete? | -- | System OK | -- |
6 |
Is the action complete? | -- | System OK | -- |
