Lexus NX: Air Mix Damper Control Servo Motor Circuit (Driver Side) (B1446)

Lexus NX Service Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System / Air Mix Damper Control Servo Motor Circuit (Driver Side) (B1446)

DESCRIPTION

The No. 1 air conditioning radiator damper servo sub-assembly (driver side air mix) sends pulse signals to inform the air conditioning amplifier assembly of the damper position. The air conditioning amplifier assembly activates the motor (normal, reverse) based on the signals to move the No. 1 air conditioning radiator damper servo sub-assembly (driver side air mix) to any position. As a result, the amount of air passing through the heater core after passing through the evaporator is adjusted, and the temperature of the air blowing toward the driver seat side is controlled.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

Note

B1446

Air Mix Damper Control Servo Motor Circuit (Driver Side)

Air mix damper position sensor value does not change even if air conditioning amplifier assembly operates No. 1 air conditioning radiator damper servo sub-assembly (driver side air mix)

  • No. 1 air conditioning radiator damper servo sub-assembly (driver side air mix)
  • Air conditioning harness assembly
  • Air conditioning amplifier assembly

Memorized (30 seconds or more)

-

HINT:

The air conditioning amplifier assembly stores the DTC of the respective malfunction if it has occurred for the period of time indicated in the brackets.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When DTC B1441, B1442, B1443 and B1446 are output at same time, there would be malfunctioning on No. 1 air conditioning radiator damper servo sub-assembly.
  • When the auxiliary battery is disconnected or the air conditioning amplifier assembly is replaced, be sure to perform servo motor initialization.

    Click here

HINT:

Confirm that no mechanical problem is present because this diagnostic code can be output when either a damper link or the damper is mechanically locked.

PROCEDURE

1.

CHECK FOR DTC

(a) Clear the DTC.

Click here

Body Electrical > Air Conditioner > Clear DTCs

(b) Check for DTC.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result

Proceed to

DTC B1446 is not output

A

DTC B1446 is output

B

DTC B1446 and B1497 are output

C

A

USE SIMULATION METHOD TO CHECK

C

GO TO DTC B1497

B

2.

READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Operate the driver side temperature adjustment switch.

(e) Enter the following menus: Body Electrical / Air Conditioner / Data List.

(f) Check the value(s) by referring to the table below.

Body Electrical > Air Conditioner > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Air Mix Servo Targ Pulse(D)

No. 1 air conditioning radiator damper servo sub-assembly (driver side air mix) target pulse

Min.: 128

Max.: 383

MAX. COLD: 257 (pulse)

MAX. HOT: 165 (pulse)

-

Air Mix Servo Actual Pulse(D)

No. 1 air conditioning radiator damper servo sub-assembly (driver side air mix) actual pulse

Min.: 128

Max.: 383

MAX. COLD: 257 (pulse)

MAX. HOT: 165 (pulse)

-

Body Electrical > Air Conditioner > Data List

Tester Display

Air Mix Servo Targ Pulse(D)

Air Mix Servo Actual Pulse(D)

OK:

When the driver side temperature adjustment switch is turned from MAX COLD to MAX HOT, the actual pulse changes following the target pulse.

Result

Proceed to

Target pulse and actual pulse do not change

A

Target pulse changes but actual pulse does not change

B

Actual pulse changes following the target pulse (When troubleshooting according to the DTC)

C

Actual pulse changes following the target pulse (When troubleshooting according to Problem Symptoms Table)

D

A

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

C

GO TO STEP 5

D

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

B

3.

CHECK NO. 1 AIR CONDITIONING RADIATOR DAMPER SERVO SUB-ASSEMBLY (DRIVER SIDE AIR MIX)

(a) Replace the No. 1 air conditioning radiator damper servo sub-assembly (driver side air mix).

Click here

HINT:

Since the servo motor cannot be inspected while it is removed from the vehicle, replace the servo motor with a new or known good one and check that the condition returns to normal.

(b) Clear the DTC.

Click here

Body Electrical > Air Conditioner > Clear DTCs

(c) Check for DTC.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result

Proceed to

DTC B1446 is not output

A

DTC B1446 is output

B

A

END (NO. 1 AIR CONDITIONING RADIATOR DAMPER SERVO SUB-ASSEMBLY IS DEFECTIVE)

B

4.

CHECK AIR CONDITIONING HARNESS ASSEMBLY

(a) Replace the air conditioning harness assembly.

Click here

HINT:

Since the air conditioning harness assembly cannot be inspected while it is removed from the vehicle, replace the air conditioning harness assembly with a new or known good one and check that the condition returns to normal.

(b) Clear the DTC.

Click here

Body Electrical > Air Conditioner > Clear DTCs

(c) Check for DTC.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result

Proceed to

DTC B1446 is not output

A

DTC B1446 is output

B

A

END (AIR CONDITIONING HARNESS ASSEMBLY IS DEFECTIVE)

B

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

5.

CHECK FOR DTC

(a) Clear the DTC.

Click here

Body Electrical > Air Conditioner > Clear DTCs

(b) Check for DTC.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result

Proceed to

DTC B1446 is not output

A

DTC B1446 is output

B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

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