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 heater 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 if 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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check |
2 |
Are all of the visual indicators illuminated and is the audible indicator ON? | -- | Go to Step 8 | Go to Step 3 |
3 |
Is the display of the heater and A/C control blank? | -- | Go to Step 5 | Go to Step 4 |
Does the heater and A/C control display only °C°F? | -- | Go to Step 9 | Go to Testing for Intermittent Conditions and Poor Connections | |
5 |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 11 |
6 | Probe the battery positive voltage circuit of the heater and A/C control with a test lamp that is connected to the ground circuit of the heater and A/C control. Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 12 |
7 | Measure the voltage from the KDD data circuit to a good ground. Does the voltage measure near the specified value? | 1 Vdc | Go to Step 16 | Go to Step 13 |
8 |
Does the voltage measure near the specified value? | 1 Vdc | Go to Step 16 | Go to Step 13 |
9 |
Does the voltage measure near the specified value? | 1 Vdc | Go to Step 10 | Go to Step 14 |
10 | Measure the frequency from the KDD clock circuit to a good ground. Does the frequency measure near the specified value? | 930 Hz | Go to Step 16 | Go to Step 15 |
11 | Repair the battery positive voltage circuit of the heater and A/C control for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | -- |
12 | Repair the ground circuit of the heater and A/C control for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | -- |
13 | Test the KDD data circuit for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 |
14 | Test the KDD data circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 15 |
15 | Test the KDD clock circuit for a short to voltage, a short to ground, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 |
16 | Inspect for poor connections at the harness connector of the heater and A/C control. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 |
17 | Inspect for poor connections at the harness connector of the heater and A/C programmer. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 |
18 | Replace the heater and A/C control. Refer to Control Assembly Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- |
19 | Replace the heater and A/C programmer. Refer to Programmer Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- |
20 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
