For 1990-2009 cars

### Circuit Description

When the A/C switch is pressed on the heater and A/C control, an internal timer begins counting the amount of time the A/C switch is being depressed. The timer stops counting when the switch is released.

### Conditions for Running the DTC

The diagnostic runs every 40 ms.

### Conditions for Setting the DTC

The A/C switch is active for at least 15 counts.

### Action Taken When the DTC Sets

The DTC is stored in memory.

### Conditions for Clearing the DTC

The DTC clears after 20 fault-free ignition cycles.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: HVAC Schematics
1 | Did you perform the HVAC Systems Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - HVAC Systems - Automatic
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, observe the A/C SWITCH parameter in the Heating and Air Conditioning data list.

Does the scan tool display INACTIVE?

--

Go to Step 3

Go to Step 4

3 |

1. Activate the A/C button on the heater and A/C control.
2. With a scan tool, observe the A/C SWITCH parameter.

Does the A/C SWITCH parameter change state?

--

System OK

Go to Step 5

4 | Does the scan tool display ACTIVE at all times? | -- | Go to Step 5 | --
5 | Important: Perform the reprogramming procedure for the HVAC Control Module Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 6 | --
6 |

1. Use the scan tool in order to clear the DTCs.
2. Press the A/C switch ON and OFF several times.

Does the DTC reset?

--

Go to Step 2

System OK