GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 DeVille 🢒 DTC 🢒 DTC B1340 Air Mix Door #1 Movement Problem
Table 1: Actuator Values

Object Number: 506751 Size: MF
HVAC Components
Cell 68: Actuators
Handling ESD Sensitive Parts Notice

Circuit Description

The heater and A/C programmer supplies voltage to an internal motor that drives the air mix door. The heater and A/C programmer monitors the air mix door position feedback from a sensor on the motor. If the air mix door is requested to move but the feedback voltage does not change, the heater and A/C programmer will store DTC B1340. If the air mix door feedback indicates that the feedback is near the hot or the cold extreme, the DTC will not set. Evaluate the operation of the air mix door through self diagnostics as described in the test description.

Conditions for Running the DTC
    • The commanded air mix door is greater than 0%.
    • The commanded air mix door is less than 76%.

Failure Conditions

The actual air mix door is not within 3% of the commanded air mix door position within approximately 60 seconds.

Notes On Intermittence

If an intermittent DTC B1340 is set, complete the following steps:

  1. Connect a Scan Tool .
  2. Select the snapshot data for the air mix door #1.
  3. Observe the value of the feedback and commanded position:
    4. 3.1. Use a Scan Tool override while monitoring the feedback value. Command the door to these positions.
    3.2. Without turning the ignition off, inspect the air mix door linkage for any obstruction at these positions.

Test Description

  1. Perform the Diagnostic System Check before continuing with the diagnosis of this DTC.

    2.

  2. A Scan Tool allows for the direct control of the air mix door by observing the following conditions:

    3. • The air mix door position feedback value
    • The value`s difference from the air mix door commanded position value

  3. These readings indicate a fault internal to the heater and A/C programmer in the air mix door sensor feedback.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. With the engine running, connect a Scan Tool .
  2. Turn the dual zone to OFF (passenger temperature offset at 0 or OFF).
  3. Exercise the suspect actuator using the temperature control on the control assembly.

Is the door being commanded (COM) to the proper high and low values?

COM High 100 %

COM Low 0 %

Go to Step 3

Go to Step 4

3

Compare the high and low actual (ACT) values.

Are the values within the specified ranges?

ACT High 100-95 %

ACT Low 0-5 %

Go to Step 6

Go to Step 5

4
  1. Inspect the terminal contact. Refer to Testing for Electrical Intermittents in Wiring Systems.
  2. If the contact is OK, replace the heater and A/C programmer. Refer to Programmer Replacement .
  3. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--

5
  1. Turn the engine OFF.
  2. Turn the ignition to the ON position.
  3. Inspect the linkage between the air mix door and the actuator.
  4. Inspect the air mix door for obstructions.

Are any of the above conditions present?

--

Go to Step 8

Go to Step 7

6
  1. Replace the heater and A/C programmer. Refer to Programmer Replacement .
  2. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--

7
  1. Disconnect the driver air mix actuator connector.
  2. Test pin 10 CKT 705 for 5 V.
  3. Test pin 5 CKT 147 for 12 V.
  4. Inspect the following circuits for an open:
    5. • CKT 1814
    • CKT 831
    • CKT 407

Are any of the actuator circuits suspect?

--

Go to Step 10

Go to Step 9

8
  1. Repair the condition.
  2. Adjust the air mix door linkage. Refer to Temperature Valve Link Adjustment - Driver .
  3. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--

9
  1. Replace the actuator. Refer to Air Mix Actuator Replacement - Driver .
  2. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--

10
  1. Repair the suspect circuit. Refer to Wiring Repairs in Wiring Systems.
  2. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--

Actuator Values

Actuator

Com High

Com Low

Act High

Act Low

Air Mix #1 (Driver)

100 %

0 %

100-95 %

0-5 %

--

250 counts

0 counts

255 counts

10 counts