B1399

Steps 1-12:

Steps 13-20:

Schematic:

CIRCUIT DESCRIPTION
The heater and A/C programmer communicates with the heater and A/C control via the Keyboard Display Driver (KDD) data bus. This communication link is only used by the heater and A/C programmer and the heater and A/C control.

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC
^ There is a loss of communications between the beater and A/C programmer and the heater and A/C control.
^ The above conditions are present for 3 seconds.

ACTION TAKEN WHEN THE DTC SETS
The heater and A/C system will be disabled.

CONDITIONS FOR CLEARING THE DTC
^ The DTC will become history it the heater and A/C programmer no longer detects a failure.
^ The history DTC will clear after 50 fault free ignition cycles.
^ The DTC can be cleared with a scan tool.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
4. This step verifies that the heater and A/C control is functioning, but not communicating with the heater and A/C programmer.