Lexus RX300 (MCU15). Manual — part 395

DI–810

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

LEXUS RX300 (RM785E)

B1442/42

(DI–844)

Air inlet damper control servomotor

S Air inlet damper control servomotor

S Air inlet damper position sensor

S Harness and connector between A/C ECU (Combination

Meter ECU) and air inlet position sensor

S Harness and connector between A/C ECU (Combination

Meter ECU) and air inlet damper control servomotor

S A/C ECU (Combination Meter ECU)

f

(15 secs. or more)

B1443/43

(DI–844)

Air outlet damper control servomotor

circuit

S Air outlet damper control servomotor

S Air outlet damper position sensor

S Harness and connector between A/C ECU (Combination

Meter ECU) and ar outlet position sensor

S Harness and connector between A/C ECU (Combination

Meter ECU) and air outlet servomotor

S A/C ECU (Combination Meter ECU)

f

(15secs. or more)

HINT:

S

*1

If the room temp. is approx. –20°C (–4°F) or lower, DTC B1411/11 may be output even though the

system is normal.

S

*2

If the ambient temperature is approx. –50°C (–58°F) or lower, a DTC may be output even though

the system is normal.

S

*

3

If the check is being performed in a dark place, DTC B1421/21 (solar sensor circuit abnormal) could

be displayed. In this case, perform DTC check again while shining a light, such as an inspection light,
on the solar sensor. If DTC B1421/21 is still displayed, there could be trouble in the solar sensor circuit.

S

*

4

Compressor lock (DTC B1422/22) is indicated only for a current malfunction. (See page DI–826)

To confirm DTC B1422/22, preform the following steps.
(1)

With the engine ON, enter the DTC check mode.

(2)

Press the R/F switch to enter actuator check mode, and set the operation to Step No. 3.

(3)

Press the AUTO switch to return to DTC check mode.

(4)

The DTC is displayed after approx. 3 secs.

S

*

5

The A/C control assembly memorizes the DTC of the respective malfunction when it occurs for peri-

od of time indicated in the brackets.

DI3FS–03

I08328

C12

C11

C10

1

2

3

4

5

6

7

8

1

2

3

4

5

6

7

8

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

9

10

11

12

13

14

15

16

9

10

11

12

13

14

15

16

17

18

19

20

21

22

18

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DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–811

LEXUS RX300 (RM785E)

TERMINALS OF ECU

Symbols (Terminals No.)

Wiring Color

Condition

STD Voltage (V)

IG ↔ GND (C12–1 ↔ C12–11)

R–W ↔ BR

IG ON.

10 – 14 V

B ↔ GND (C12–3 ↔ C12–11)

W–L ↔ BR

Constant

10 – 14 V

BLW ↔ GND

(C12–4 ↔ C12–11)

P–L ↔ BR

IG ON. Turn the blower SW ON.

1 – 3 V

TAM ↔ SG–5

B R ↔ W R

Ambient temp.: 25 °C (77 °F)

1.35 – 1.75 V

TAM ↔ SG 5

(C12–7 ↔ C12–16)

B–R ↔ W–R

Ambient temp.: 40 °C (104 °F)

0.85 – 1.25 V

TR ↔ SG 3 (C11 3 ↔ C11 9)

G R ↔ G W

Room temp.: 25 °C (77 °F)

1.8 – 2.2 V

TR ↔ SG–3 (C11–3 ↔ C11–9)

G–R ↔ G–W

Room temp.: 40 °C (104 °F)

1.2 – 1.6 V

TPI ↔ SG–2

GR ↔ B W

Push REC switch.

3.5 – 4.5 V

TPI ↔ SG 2

(C11–11 ↔ C11–1)

GR ↔ B–W

Push FRS switch

0.5 – 1.5 V

AIR ↔ GND

R ↔ BR

Push FRS switch

10 – 14 V

AIR ↔ GND

(C11–12 ↔ C12–11)

R ↔ BR

Push REC switch

Below 1.0 V

AIF ↔ GND

BR Y ↔ BR

Push FRS switch

Below 1.0 V

AIF ↔ GND

(C11–13 ↔ C12–11)

BR–Y ↔ BR

Push REC switch

10 – 14 V

TS ↔ S5–3

Y B ↔ L

Sensor subjected to electric light

0.8 – 4.3 V

TS ↔ S5 3

(C11–15 ↔ C11–16)

Y–B ↔ L

Sensor covered by a cloth

Below 0.8 V

TE ↔ SG–1

G W ↔ B R

Evaporator temp.: 0 °C (32 °F)

2.0 – 2.4 V

TE ↔ SG 1

(C10–2 ↔ C10–10)

G–W ↔ B–R

Evaporator temp.: 15 °C (59 °F)

1.4 – 1.8 V

TPO ↔ SG–1

LG R ↔ B R

IG ON. Air outlet mode: FACE

3.5 – 4.5 V

TPO ↔ SG 1

(C10–4 ↔ C10–10)

LG–R ↔ B–R

IG ON. Push front DEF switch.

0.5 – 1.5 V

AOD ↔ GND

LG B ↔ BR

IG ON. Air outlet mode: FACE

Below 1.0 V

AOD ↔ GND

(C10–5 ↔ C12–11)

LG–B ↔ BR

IG ON. Air outlet mode: DEF

10 – 14 V

AOF ↔ GND

R W ↔ BR

IG ON. Air outlet mode: FACE

10 – 14 V

AOF ↔ GND

(C10–6 ↔ C12–11)

R–W ↔ BR

IG ON. Air outlet mode: DEF

Below 1.0 V

TP ↔ SG–1

R L ↔ B R

IG ON. Temp. control switch: Max. COOL

3.5 – 4.5 V

TP ↔ SG 1

(C10–7 ↔ C10–10)

R–L ↔ B–R

IG ON. Temp. control switch: Max. HOT

0.5 – 1.5 V

AMH ↔ GND

Y R ↔ BR

IG ON. Temp. control switch: Max. HOT

10 – 14 V

AMH ↔ GND

(C10–8 ↔ C12–11)

Y–R ↔ BR

IG ON. Temp. control switch: Max. COOL

Below 1.0 V

AMC ↔ GND

Y B ↔ BR

IG ON. Temp. control switch: Max. COOL

10 – 14 V

AMC ↔ GND

(C10–9 ↔ C12–11)

Y–B ↔ BR

IG ON. Temp. control switch: Max. HOT

Below 1.0 V

DI3FT–02

DI–812

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DIAGNOSTICS

AIR CONDITIONING SYSTEM

LEXUS RX300 (RM785E)

PROBLEM SYMPTOMS TABLE

Symptom

Suspect Area

See page

Whole functions of the A/C system does not operate

1. A/C ECU (Combination meter ECU)

2. IG power source circuit

IN–32

Air Flow Control: No blower operation

1. IG power source circuit

2. Heater main relay

3. Body ECU

4. Blower motor circuit

5. Blower motor controller

4. A/C ECU (Combination meter ECU)

AC–71

DI–676

DI–852

DI–852

IN–32

Air Flow Control: No blower control

1. Heater main relay

2. Body ECU

3. Blower motor circuit

4. Blower motor controller

5. A/C ECU (Combination meter ECU)

AC–71

DI–676

DI–852

DI–852

IN–32

Air Flow Control: Insufficient air flow

1. Blower motor circuit

2. Blower moto controller

DI–852

DI–852

Temperature Control: No cool air comes out

1. Refrigerant volume

2. Drive belt tension

3. Refrigeration system inspection with manifold gauge set

4. Compressor circuit

5. Pressure switch circuit

6. Compressor lock sensor circuit

7. Air mix damper position sensor circuit

8. Air mix damper control servomotor circuit

9. Room temp. sensor circuit

10. Ambient temp. sensor circuit

11. A/C ECU (Combination meter ECU)

AC–22

AC–15

AC–3

DI–855

DI–829

DI–826

DI–832

DI–841

DI–814

DI–817

IN–32

Temperature Control: No warm air comes out

1. Air mix damper position sensor circuit

2. Air mix damper control servomotor circuit

3. Room temp. sensor circuit

4. Ambient temp. sensor circuit

5. Evaporator temp. sensor circuit

6. A/C ECU (Combination meter ECU)

DI–832

DI–841

DI–814

DI–817

DI–820

IN–32

Temperature Control: Output air is warmer or cooler that the set

temperature or response is slow

1. Refrigerant volume

2. Drive belt tension

3. Refrigeration system inspection with manifold gauge set

4. Cooling fan system

5. Solar sensor circuit

6. Room temp. sensor circuit

7. Ambient temp. sensor circuit

8. Evaporator temp. sensor circuit

9. Air mix damper position sensor circuit

10. Air mix damper control servomotor circuit

11. Air inlet damper position sensor circuit

12. Air inlet damper control servomotor circuit

13. Condenser

14. Evaporator

15. Heater radiator

16. Expansion valve

17. A/C ECU (Combination meter ECU)

AC–22

AC–15

AC–3

CO–25

DI–823

DI–814

DI–817

DI–820

DI–832

DI–841

DI–835

DI–844

AC–52

AC–23

AC–23

AC–58

IN–32

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–813

LEXUS RX300 (RM785E)

Symptom

Suspect Area

See page

Temperature Control: No temperature control (only Max. cool or

Max. warm)

1. Room temp. sensor circuit

2. Ambient temp. sensor circuit

3. Air mix damper position sensor circuit

4. Air mix damper control servomotor circuit

5. A/C ECU (Combination meter ECU)

DI–814

DI–817

DI–832

DI–841

IN–32

No air inlet control

1. Air inlet damper position sensor circuit

2. Air inlet damper control servomotor circuit

3. A/C ECU (Combination meter ECU)

DI–835

AC–52

IN–32

No air flow mode

1. Air outlet damper position sensor circuit

2. Air outlet damper control servomotor circuit

3. A/C ECU (Combination meter ECU)

DI–838

DI–847

IN–32

Engine idle up does not occur, or is continuous

1. Compressor circuit

2. ECM

DI–855

IN–32

Blinking of A/C indicator

1. Compressor circuit

2. Compressor lock sensor circuit

2. A/C ECU (Combination meter ECU)

DI–855

DI–826

IN–32

Set temp. value displayed does not change up with operation of

temp. control switch.

A/C ECU (Combination meter ECU)

IN–32

DTC not recorded.

Set mode is cleared when IG switch is turned off.

1. Back–up power source circuit

2. Combination meter ECU

DI–850

IN–32