GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 Seville 🢒 DTC 🢒 DTC B1344

Circuit Description

The HVAC control module (IPM) commands the mode actuator to move by controlling the voltage on the control circuit. A low voltage of 0 volts moves the door toward the defrost position, 2.5 volts stops the motor, 5 volts moves the door toward the vent position. The IPM determines the current position of the actuator by monitoring the voltage on the feedback circuit. The feedback potentiometer is a function of the motor position. A high voltage of 4-5 volts indicates the vent position. A low voltage of less than 1 volt indicates the defrost position. The IPM controls the mode actuator door positions in order to maintain the selected air outlet.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The IPM detects the signal circuit is less than 5 counts (0.09 V) or greater than 250 counts (4.90 V).

Action Taken When the DTC Sets

A default value will be used for the sensor data by the IPM to move the mode actuator.

Conditions for Clearing the DTC
    • The DTC will become history if the IPM 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.

Diagnostic Aids

Check the following conditions:

    • A disconnected or broken door may also set this DTC by allowing the mode actuator to travel to its internal stops (overtravel condition).
    • Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

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

    2.

  2. 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.

    3.

  3. Tests for a short to ground in the 5-volt reference circuit.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

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 Mode Door Actual parameter in the Instrument Panel Module HVAC Door Positions data list.

Does the scan tool indicate that the Mode Door Actual parameter is within the specified range?

5-250 counts (0.09-4.90 V)

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the mode actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Mode Door Actual parameter.

Does the scan tool indicate that the Mode Door Actual parameter is greater than the specified value?

250 counts (4.90 V)

Go to Step 4

Go to Step 8

4

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the signal circuit of the mode actuator and the low reference circuit of the mode actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Mode Door Actual parameter.

Does the scan tool indicate that the Mode Door Actual parameter is less than the specified value?

5 counts (0.09 V)

Go to Step 5

Go to Step 9

5

  1. Turn OFF the ignition.
  2. Disconnect the fused jumper wire.
  3. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the mode actuator and the signal circuit of the mode actuator.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, observe the Mode Door Actual parameter.

Does the scan tool indicate that the Mode Door Actual parameter is greater than the specified value?

250 counts

Go to Step 7

Go to Step 6

6

Test the 5-volt reference circuit of the mode actuator 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 15

Go to Step 12

7

Test the 5-volt reference circuit of the mode actuator 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 15

Go to Step 11

8

Test the signal circuit of the mode actuator 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 15

Go to Step 12

9

Test the signal circuit of the mode actuator 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 15

Go to Step 10

10

Test the low reference circuit of the mode actuator 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 15

Go to Step 12

11

Inspect for poor connections at the harness connector of the mode actuator. 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 15

Go to Step 13

12

Inspect for poor connections at the harness connector of the IPM. 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 15

Go to Step 14

13

Important: Perform the recalibration procedure for the mode actuator.

Replace the mode actuator. Refer to Mode Actuator Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Important: Perform the recalibration procedure for the IPM.

Replace the IPM. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

--

Go to Step 15

--

15
  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