GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2003 🢒 LeSabre 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B0490

Circuit Description

The right air temperature switch assembly consists of simple momentary contact switches that connect a series of resistors so that each switch selection corresponds to a fixed resistance value. The front passenger door module (FPDM) determines which switch has been pressed by the voltage drop across the corresponding resistance value. The FPDM converts this input to a digital signal and communicates it to the driver door module (DDM) over the simple bus interface (SBI). The DDM is responsible for the class 2 interface and setting the DTC.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC
    • The DDM detects that the right air temperature switch signal circuit of the right air temperature switch assembly is less than 0.09 volt (5 counts) or greater than 4.90 volts (250 counts).
    • The DDM detects that the right air temperature switch assembly is active for more than 30 seconds.

Action Taken When the DTC Sets

The DDM will ignore the switch command.

Conditions for Clearing the DTC
    • The DTC will become history if the DDM no longer detects a failure.
    • The history DTC will clear after 50 fault-free ignition cycles.
    • Use the scan tool in order to clear the DTCs.

Diagnostic Aids
    • If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • When the warmer (red) switch is active, the input to the DDM is 2.50-3.09 volts (127-158 counts).
    • When the cooler (blue) switch is active, the input to the DDM is 0.99-1.58 volts (51-81 counts).
    • When neither switch is active, the input to the DDM is 3.99-4.58 volts (204-234 counts).

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The value given is the normal condition that exists when no switch is activated.

    2.

  2. Tests for the proper operation of the circuit in the high voltage range.

    3.

  3. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC 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 Pass. HVAC Switch parameter in the Driver Door Module data list.

Does the scan tool indicate that the Pass. HVAC Switch parameter is within the specified range?

204-234 counts

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the right air temperature switch assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Pass. HVAC Switch parameter.

Does the scan tool indicate that the Pass. HVAC Switch parameter is greater than the specified value?

250 counts

Go to Step 4

Go to Step 5

4

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the right air temperature switch signal circuit and the low reference circuit of the right air temperature switch assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Pass. HVAC Switch parameter.

Does the scan tool indicate that the Pass. HVAC Switch parameter is less than the specified value?

5 counts

Go to Step 8

Go to Step 6

5

Test the right air temperature switch signal circuit of the right air temperature switch assembly 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 12

Go to Step 9

6

Test the right air temperature switch signal circuit of the right air temperature switch assembly for a short to voltage, 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 12

Go to Step 7

7

Test the low reference circuit of the right air temperature switch assembly 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 12

Go to Step 9

8

Inspect for poor connections at the harness connector of the right air temperature switch assembly. 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 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the front passenger door module. 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 12

Go to Step 11

10

Replace the right air temperature switch assembly. Refer to Air Temperature Switch Assembly Replacement - Right Side .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the front passenger door module. Refer to Door Control Module Replacement in Doors.

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK