GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2004 🢒 Seville 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B1340, B1341, B1343, or B1344

Circuit Description
    • DTC B1340 - Left Air Temperature Actuator
    • DTC B1341 - Right Air Temperature Actuator
    • DTC B1343 - Recirculation Actuator
    • DTC B1344 - Mode Actuator

The HVAC control module (IPM) commands the actuator to move by controlling the voltage supplied on the control circuit. A low voltage of 0 volts moves the door in one direction. A voltage of 2.5 volts stops the door. A high voltage of 5 volts moves the door in the opposite direction. The IPM determines the current position of the actuator by monitoring the voltage on the signal circuit. The feedback potentiometer is a function of the motor position.

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 in an attempt to maintain actuator operation.

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 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

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

Does the scan tool indicate that the 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 appropriate actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the parameter.

Does the scan tool indicate that the 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 appropriate actuator and the low reference circuit of the actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the parameter.

Does the scan tool indicate that the 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 appropriate actuator and the signal circuit of the actuator.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, observe the parameter.

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

250 counts (4.90 V)

Go to Step 7

Go to Step 6

6

Test the 5-volt reference circuit of the appropriate 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 appropriate 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 appropriate 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 appropriate 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 appropriate 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 appropriate 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 appropriate actuator.

Replace the appropriate actuator. Refer to Air Temperature Actuator Replacement - Right Side , Air Temperature Actuator Replacement - Left Side , Mode Actuator Replacement or Recirculation 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