Lexus RX300 (MCU15). Service manual - part 397

I08332

TAM

SG–5

(+)

(–)

DI–818

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

HINT:
In case of using the hand–held tester, start the inspection step 1 and in case of not using the hand–held
tester, start form step 2.

1

Check ambient temp. sensor using hand–held tester.

PREPARATION:
Connect the hand–held tester to the DLC3.
CHECK:
Check the ambient temp. sensor using DATA LIST.

OK

Check and replace A/C ECU (Combination me-
ter ECU).

NG

2

Check voltage between terminals TAM and SG–5 of A/C ECU (combination meter
ECU).

PREPARATION:
Remove A/C ECU with connectors still connected.
CHECK:
(a)

Turn ignition switch ON.

(b)

Measure voltage between terminals TAM and SG–5 of
A/C ECU connector at each temperature.

OK:

Voltage :
at 25

°C (77°F) : 1.35 – 1.75 V

at 40

°C (104°F) : 0.85 – 1.25 V

HINT:
As the temperature increases, the voltage decreases.

NG

Go to step 3.

OK

Proceed to next circuit inspection shown on problem symptoms table (See page DI–812).  Howev-
er, if DTC B1412/12 is displayed, check and replace ECM and A/C ECU (Combination meter ECU).

I08333

2

1

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–819

LEXUS RX300   (RM785E)

3

Check ambient temperature sensor.

PREPARATION:
Disconnect ambient temperature sensor connector.
CHECK:
Measure resistance between terminals 1 and 2 of ambient tem-
perature sensor connector at each temperature.
OK:

Resistance :
at 25

°C (77°F) : 1.6 – 1.8 kΩ

at 50

°C (122°F) : 0.5 – 0.7 kΩ

HINT:
As the temperature increases, the resistance decreases.
NOTICE:
When installing the ambient temperature sensor, be sure to
connect the sensor connector before connecting the bat-
tery.

NG

Replace ambient temperature sensor.

OK

4

Check harness and connector between A/C ECU (combination meter ECU) and
ambient temperature sensor (See page IN–32).

NG

Repair or replace harness or connector.

OK

Check and replace A/C ECU (Combination
meter ECU).

I08334

A17 
Evaporator
Temp. Sensor

1

2

B–Y

10

5 V

A/C ECU (Combina-
tion meter ECU)

TE

SG–1

B–R

6

IF1

IF1

4

G–Y

G–W

2

C10

C10

DI–820

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

LEXUS RX300   (RM785E)

DTC

B1413/13 Evaporator Temperature Sensor circuit

CIRCUIT DESCRIPTION

This sensor detects the temperature inside the cooling unit and sends the appropriate signals to the A/C ECU
(Combination meter ECU).

DTC No.

Detection Item

Trouble Area

B1413/13

Open or short in evaporator temperature sensor circuit.

S Evaporator temperature sensor.

S Harness or connector between evaporator temperature sen-

sor and A/C ECU (Combination meter ECU).

S A/C ECU (Combination meter ECU).

WIRING DIAGRAM

DI3FW–03

I08335

TE

SG–1

(+)

(–)

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–821

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

HINT:
In case of using the hand–held tester start the inspection step 1 and in case of not using the hand–held tester,
start form step 2.

1

Check evaporator temp. sensor using hand–held tester.

PREPARATION:
Connect the hand–held tester to the DLC3.
CHECK:
Check the evaporator temp. sensor using DATA LIST.

OK

Check and replace A/C ECU (Combination me-
ter ECU).

NG

2

Check voltage between terminals TE and SG–1 of A/C ECU (Combination meter
ECU) connector.

PREPARATION:
Remove A/C ECU with connectors still connected.
CHECK:
(a)

Turn ignition switch ON.

(b)

Measure voltage between terminals TE and SG–1 of A/C
ECU connector at each temperature.

OK:

Voltage :
at 0

°C (32°F) : 2.0 – 2.4 V

at 15

°C (59°F) : 1.4 – 1.8 V

HINT:
As the temperature increases, the voltage decreases.

NG

Go to step 3.

OK

Proceed to next circuit inspection shown on problem symptorms table (See page DI–812).  How-
ever, if DTC B1413/13 is displayed, check and replace A/C ECU (Combination meter ECU).