Lexus ES300 (1997 year). Manual - part 444

N15622

1

2

N02774

20 msec/Division (Idling)

LOCK IN signal waveform

0 V

0.2 V/Din.

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–553

705

1997 LEXUS ES300   (RM511U)

2

Check compressor lock sensor.

PREPARATION:
Disconnect compressor lock sensor connector.
CHECK:
Measure resistance between terminals 1 and 2 of compressor
lock sensor connector.
OK:

Resistance: at 20 

°

C (68 

°

F): 65 – 125 

Ω

Reference: Inspection using oscilloscope

During cranking or idling, measure voltage between terminals
LOCK IN and SG of A/C control assembly.
HINT:
The correct waveform appears as shown in the illustration on
the left.

NG

Replace compressor lock sensor.

OK

3

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

IN–27

).

NG

Repair or replace harness or connector.

OK

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

DI–535

). However, if DTC 22

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

I00327

A/C Control Assembly

12 V

PSW

A14

9

L–B

IM3

12

Pressure Switch

W–B

EC

L–B

4

1

DI–554

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

706

1997 LEXUS ES300   (RM511U)

DTC

   23

Pressure Switch Circuit

CIRCUIT DESCRIPTION

This pressure switch sends the appropriate signals to the A/C control assembly when the air conditioning
refrigerant pressure drops too low or rises too high. When the A/C control assembly receives these signals,
if outputs signals via the ECM to switch off the compressor relay and turns the magnetic clutch off.

DTC No.

Detection Item

Trouble Area

23

Open in pressure sensor circuit.

Abnormal refrigerant pressure.

below 196 kPa (2.0 kgf/cm

2,

 28 psi)

over 3,140 kPa (32.0 kgf/cm

2

, 455 psi)

Pressure switch

Harness or connector between pressure switch and A/C con-

trol assembly.

Refrigerant  pipe line.

A/C control assembly.

WIRING DIAGRAM

DI0DE–01

BE3840

I00368

I00370

ON

PSW(+)

(–)

Low Pressure Cut Side

Reference: High Pressure Cut Side

ON (0 V)

225 kPa

196 kPa

OFF (12 V)

2,550 kPa

3,140 kPa

OFF (12 V)

ON (0 V)

I00379

Low Pressure Cut Side

Reference: High Pressure Cut Side

ON (continuity

225 kPa

196 kPa

OFF (no continuity

2,550 kPa

3,140 kPa

OFF (no continuity)

ON (continuity)

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–555

707

1997 LEXUS ES300   (RM511U)

INSPECTION PROCEDURE

1

Check voltage between terminals PSW of A/C control assembly and body
ground.

PREPARATION:
(a)

Install the manifold gauge set (See page 

AC–17

).

(b)

Turn ignition switch ON.

CHECK:
Check voltage between terminals PSW of A/C control assembly
connector and body ground when air conditioning gas pressure
is changed.
OK:

The voltage changes with gas pressure, as shown in
the diagram below.

OK

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

DI–535

).

NG

2

Check pressure switch.

PREPARATION:
Disconnect pressure switch connector.
CHECK:
Check continuity between terminals 1 and 4 of pressure switch
when air conditioning gas pressure is changed.
OK:

The continuity changes with gas pressure as shown
below.

NG

Replace pressure switch.

OK

DI–556

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

708

1997 LEXUS ES300   (RM511U)

3

Check harness and connector between A/C control assembly and pressure
switch, pressure switch and body ground (See page 

IN–27

).

NG

Repair or replace harness or connector.

OK

Check and replace A/C control assembly.