Lexus ES300 (1997 year). Manual — part 442

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–545

697

1997 LEXUS ES300 (RM511U)

3

Check harness and connector between A/C control assembly and evaporator
temperature sensor (See page

IN–27

).

NG

Repair or replace harness or connector.

OK

Check and replace A/C control assembly.

I00365

A/C Control Assembly

5 V

TW2

A14

14

V

ECM

E10–9

DI–546

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

698

1997 LEXUS ES300 (RM511U)

DTC

14

Engine Coolant Temperature Sensor Circuit

CIRCUIT DESCRIPTION

This sensor detects the engine coolant temperature and sends the appropriate signals to the A/C control
assembly. These signals are used for warm up control when the engine is cold.

DTC No.

Detection Item

Trouble Area

14

Open or short in ECT sensor circuit.

ECT sensor

Harness or connector between ECT sensor and A/C control

assembly

A/C control assembly

WIRING DIAGRAM

DI0DB–01

BE3840

I00398

I00369

ON

TW(+)

SG(–)

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–547

699

1997 LEXUS ES300 (RM511U)

INSPECTION PROCEDURE

1

Check voltage between terminals TW and SG of A/C control assembly connector.

PREPARATION:
(a)

Remove A/C control assembly with connectors still con-
nected (See page

BO–79

).

(b)

Turn ignition switch ON.

CHECK:
Measure voltage between terminals TW and SG of A/C control
assembly connector at each temperature.
OK:

Voltage
at 0

°C

(32

°

F): 2.8 – 3.2 V

at 40

°

C (104

°

F): 1.8 – 2.2 V

at 70

°

C (158

°

F): 0.9 – 1.3 V

HINT:
As the temperature increases, the voltage decreases.

NG

Go to step 2

OK

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

DI–535

). However, if DTC 14

is displayed, check and replace A/C control assembly.

N15619

DI–548

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

700

1997 LEXUS ES300 (RM511U)

2

Check engine coolant temperature sensor.

PREPARATION:
(a)

Remove A/C unit (See page

AC–23

).

(b)

Remove engine coolant temperature sensor.

CHECK:
Measure resistance between terminals 1 and 2 of engine cool-
ant temperature sensor connector at each temperature.
OK:

Resistance
at 0

°C

(32

°

F): 50 k

Ω

or less

at 40

°

C (104

°

F): 2.5 – 2.7 k

Ω

at 100

°

C (212

°

F): 0.2 k

Ω

or more

HINT:
As the temperature increases, the voltage decreases.

NG

Replace engine coolant temperature sensor.

OK

3

Check harness and connector between A/C control assembly and ECT sensor
(See page

IN–27

).

NG

Repair or replace harness or connector.

OK

Check and replace A/C control assembly.