Circuit Description
DTC 55 is an internal control unit hardware failure (RAM, ROM defective)
in the heater and A/C control.
Conditions for Setting the DTC
| • | The heater and A/C control detects an internal hardware malfunction. |
| • | The heater and A/C control checks the hardware on a continuous
basis every 200 ms. |
Action Taken When the DTC Sets
| • | Stores a DTC 55 in the controllers memory. |
| • | Disables all heater and A/C control functions. |
Conditions for Clearing the DTC
| • | The condition for the fault is no longer present. |
| • | The use of a scan tool. |
| • | A history DTC will clear after 20 consecutive ignition cycles
if the condition for the fault is no longer present. |
Diagnostic Aids
Because a DTC 55 is an internal malfunction to the controller, the repair
procedure is to replace the heater and A/C control. Program the new heater
and A/C control. Refer to Heater and A/C Control Replacement for the programming
procedure.
