Lexus SC300 / Lexus SC400. Manual - part 26

Diag. Code 32, 42

Air Inlet Damper Position Sensor Circuit

CIRCUIT DESCRIPTION

This sensor detects the position of the air inlet
damper and sends the appropriate signals to the
air conditioner control assembly.
The position sensor is built into the air mix servo-
motor assembly.

Code No.

Diag. Code Detecting Condition

Trouble area

32

Short to ground or power source circuit in air
inlet damper position sensor circuit.

Air inlet damper position sensor.

Harness or connector between air inletser-
vomotor assembly and A/C controlassem-

42

Air inlet damper position sensor value does not
change even if A/C control assembly operates
air inlet servomotor.

vomotor assembly and A/C controlassem-
bly

A/C control assembly

DIAGNOSTIC CHART

Check voltage between terminals TP1 and SG

of  air conditioner control assembly 

connector.

Check air inlet damper position sensor.

Check harness and connector between air

conditioner control assembly and air inlet
servomotor assembly (See page 

IN–27

).

Check and replace air conditioner control 

assembly.

Proceed to next circuit inspection

shown on matrix chart (See page

AC-36

). However, when Diag.

code 32 or 42 is displayed, check
and replace air conditioner control

assembly.

Replace air inlet servomotor
assembly.

Repair or replace harness or

connector.

AC–62

–

AIR CONDITIONING SYSTEM

Troubleshooting

Check  voltage between terminals TP1 and SG of air conditioner control

assembly connector.

(1)

Remove console upper panel.
(See page 

BO-111

).

(2)

Remove A/C control assembly with connec–
tors still connected.

(3)

Turn ignition switch ON.

Press REC/FRS switch to change the air inlet
between fresh and recirculation air, and measure
voltage between terminals TP1 and SG of air
conditioner control assembly  when the air inlet
servomotor operates.

In addition, as the air inlet servomotor is moved
from REC side to FRS side, the voltage de-
creases gradually without  interruption.

Proceed to next circuit inspection shown on matrix chart
(See page 

AC-36

).However, when Diag. code 32 or 42 is

displayed, check and replace air conditioner control  assem-
bly.

Check air inlet damper position sensor.

(1)

Remove heater unit. (See page 

AC-127

)

(2)

Disconnect air inlet servomotor assembly
connector.

Measure resistance between terminals S5 and SG of
air  inlet servomotor assembly connector.

Resistance:        4.7~7.2  k

While operating air inlet servomotor as in the
procedure on page 

AC-65

, measure  resistance

between terminals TP1 and SG of air inlet servo-
motor assembly connector.

Resistance:

As the air inlet servomotor moves from REC side
to FRS side, the  resistance decreases gradually
without  interruption.

Replace  air inlet servomotor assembly.

Check for open and short in harness and connector between air conditioner
control assembly and air inlet servomotor assembly (See page 

IN-27

).

Repair or replace harness or connector.

Check and replace air conditioner control assembly.

INSPECTION PROCEDURE

–

AIR CONDITIONING SYSTEM

REPAIR INSTRUCTIONS

AC–63

Diag. Code 42

Air Inlet Servomotor Circuit

CIRCUIT DESCRIPTION

The air inlet servomotor is controlled by the air conditioner control assembly and moves the air inlet
damper to the desired position.

Code No.

Diag. Code Detecting Condition

Trouble area

42

Air inlet damper position sensor value does
not change even if A/C control assembly oper-
ated air inlet servomotor

Air inlet damper position sensor.

Harness or connector between air inlet ser-
vomotor assembly and A/C control assem-
bly.

A/C control assembly

DIAGNOSTIC CHART

Actuator check.

Check air inlet servomotor.

Check harness and connector between air

conditioner control assembly and air inlet ser-
vomotor assembly (See page 

IN-27

).

Check and replace air conditioner control 

assembly.

Proceed to next circuit inspection

shown on matrix chart (See page

AC-36

).

Replace air inlet servomotor
assembly.

Repair or replace harness or

connector.

AC–64

–

AIR CONDITIONING SYSTEM

Troubleshooting

Actuator check.

Proceed to next circuit inspection shown on
matrix chart (See page 

AC-36

).

Check air inlet servomotor.

Remove cooling unit.

Connect positive 

 lead to terminal 6 and negative 



lead to terminal 2.

The lever moves smoothly to REC position.

Connect negative 



 lead to terminal 6 and positive 

lead to terminal 2.

The lever moves smoothly to FRS position.

Replace  air inlet servomotor assembly.

Check for open and short in harness and connector between air conditioner
control assembly and air inlet servomotor assembly (See page 

IN-27

).

Repair or replace harness or connector.

Check and replace air conditioner control
assembly.

(1)

Remove glove box to see and check the air
inlet damper operation

(2)

Set to the actuator check mode
(See page  

AC–30

.

(3)

Press the FRS switch and check it to step
operation.

Press the FRS switch and change it to step opera-
tion.

INSPECTION PROCEDURE

–

AIR CONDITIONING SYSTEM

Troubleshooting

AC–65