Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Air Inlet Damper Control Servo Motor Circuit (B1442/42)

DESCRIPTION

The No. 1 blower damper servo sub-assembly 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 air inlet mode selection No. 1 blower damper servo sub-assembly to the appropriate position, which controls the air inlet mode (fresh, recirculation/fresh, and recirculation).

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
B1442/42	Air Inlet Damper Control Servo Motor Circuit	Air inlet damper position sensor value does not change even if air conditioning amplifier assembly operates No. 1 blower damper servo sub-assembly	No. 1 blower damper servo sub-assembly 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 recirculation/fresh 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 Inlet Damper Targ Pulse	No. 1 blower damper servo sub-assembly target pulse	Min.: 128 Max.: 383	Recirculation: 256 (pulse) Fresh: 220 (pulse)	-
Air Inlet Damper Actual Pulse	No. 1 blower damper servo sub-assembly actual pulse	Min.: 128 Max.: 383	Recirculation: 256 (pulse) Fresh: 220 (pulse)	-

Body Electrical > Air Conditioner > Data List

Tester Display
Air Inlet Damper Targ Pulse
Air Inlet Damper Actual Pulse

OK:

When the recirculation/fresh switch is operated, 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 5

D

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

A

2.	REPLACE NO. 1 BLOWER DAMPER SERVO SUB-ASSEMBLY

(a) Replace the No. 1 blower 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 B1442/42 is output	A
DTC B1442/42 is not output	B

B

END (NO. 1 BLOWER DAMPER SERVO SUB-ASSEMBLY WAS DEFECTIVE)

A

3.	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 B1442/42 is output	A
DTC B1442/42 is not output	B

B

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

A

4.	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 B1442/42 is output	A
DTC B1442/42 is not output	B

A

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

B

END (AIR CONDITIONING HARNESS ASSEMBLY WAS DEFECTIVE)

5.	RECONFIRM DTC OUTPUT

(a) Check for DTCs.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result	Proceed to
DTC B1442/42 is output	A
DTC B1442/42 is not output	B

A

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

B

USE SIMULATION METHOD TO CHECK