Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Air Mix Damper Control Servo Motor Circuit (Rear) (B1447/47)

DESCRIPTION

The Rear No. 2 cooling unit 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 Rear No. 2 cooling unit damper servo sub-assembly 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
B1447/47	Air Mix Damper Control Servo Motor Circuit (Rear)	Air outlet damper position does not change when the air conditioning amplifier assembly operates the Rear No. 2 cooling unit damper servo sub-assembly.	Rear No. 2 cooling unit damper servo sub-assembly No. 2 air conditioning harness assembly Air conditioning amplifier assembly Harness or connector	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 parentheses.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When the battery is disconnected, or the servo motor or air conditioning amplifier assembly is replaced, be sure to perform servo motor initialization.

Click here

HINT:

Confirm that there are no mechanical problems because this DTC may be stored 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 rear passenger side temperature adjustment switch.

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

Body Electrical > Air Conditioner > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Air Mix Servo Targ Pulse(R)	Rear No. 2 cooling unit damper servo sub-assembly target pulse	Min.: 128 Max.: 383	MAX COLD: 254 (pulse) MAX HOT: 299 (pulse)	-
Air Mix Servo Actual Pulse(R)	Rear No. 2 cooling unit damper servo sub-assembly actual pulse	Min.: 128 Max.: 383	MAX COLD: 254 (pulse) MAX HOT: 299 (pulse)	-

Body Electrical > Air Conditioner > Data List

Tester Display
Air Mix Servo Targ Pulse(R)
Air Mix Servo Actual Pulse(R)

OK:

The display is as specified in the normal condition column.

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

2.	CHECK REAR NO. 2 COOLING UNIT DAMPER SERVO SUB-ASSEMBLY

(a) Replace the Rear No. 2 cooling unit 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) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / Air Conditioner / Trouble Codes.

(f) Clear the DTC.

Body Electrical > Air Conditioner > Clear DTCs

(g) Check for DTCs.

Body Electrical > Air Conditioner > Trouble Codes

OK:

DTC B1447/47 is not output.

OK

END (REAR NO. 2 COOLING UNIT DAMPER SERVO SUB-ASSEMBLY IS DEFECTIVE)

NG

3.	CHECK HARNESS AND CONNECTOR (NO. 2 AIR CONDITIONING HARNESS ASSEMBLY - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect the R52 No. 2 air conditioning harness assembly connector.

(b) Disconnect the J48 air conditioning amplifier assembly connector.

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
R52-2 (RBUG) - J48-2 (RBUG)	Always	Below 1 Ω
R52-3 (RBUS) - J48-22 (RBUS)	Always	Below 1 Ω
R52-4 (RBBU) - J48-3 (RBBU)	Always	Below 1 Ω
R52-2 (RBUG) or J48-2 (RBUG) - Other terminals and body ground	Always	10 kΩ or higher
R52-3 (RBUS) or J48-22 (RBUS) - Other terminals and body ground	Always	10 kΩ or higher
R52-4 (RBBU) or J48-3 (RBBU) - Other terminals and body ground	Always	10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.	CHECK NO. 2 AIR CONDITIONING HARNESS ASSEMBLY

(a) Replace the No. 2 air conditioning harness assembly.

Click here

(b) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / Air Conditioner / Trouble Codes.

(f) Clear the DTC.

Body Electrical > Air Conditioner > Clear DTCs

(g) Check for DTCs.

Body Electrical > Air Conditioner > Trouble Codes

OK:

DTC B1447/47 is not output.

OK

END (NO. 2 AIR CONDITIONING HARNESS ASSEMBLY IS DEFECTIVE)

NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

5.	CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Trouble Codes.

(e) Clear the DTC.

Body Electrical > Air Conditioner > Clear DTCs

(f) Check for DTCs.

Body Electrical > Air Conditioner > Trouble Codes

OK:

DTC B1447/47 is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY