Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual: Air Mix Damper Control Servo Motor Circuit (Driver Side) (B1446/46)

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 or reverse) based on these signals to move the No. 1 air conditioning radiator damper servo sub-assembly (driver side air mix) to the appropriate 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 side is controlled.

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Memory
B1446/46	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 sec. or more)*

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

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

PROCEDURE

1.	READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the engine 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) Read the Data List according to the display on the Techstream.

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 changes but actual pulse does not change	A
Target pulse and actual pulse do 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

B

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

C

GO TO STEP 4

D

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

A

2.	REPLACE NO. 1 AIR CONDITIONING RADIATOR DAMPER SERVO SUB-ASSEMBLY

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

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) Check for DTCs.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result	Proceed to
DTC B1446/46 is output	A
DTC B1446/46 is not output	B

B

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

A

3.	REPLACE 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) Check for DTCs.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result	Proceed to
DTC B1446/46 is output	A
DTC B1446/46 is not output	B

A

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

B

END (AIR CONDITIONING HARNESS ASSEMBLY WAS DEFECTIVE)

4.	RECONFIRM DTC OUTPUT

(a) Check for DTCs.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result	Proceed to
DTC B1446/46 is output	A
DTC B1446/46 is not output	B

A

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

B

USE SIMULATION METHOD TO CHECK