Lexus RX300 (MCU15). Service manual — part 399

I08338

Engine and ECT ECU

LCKI

E10

10

W–L

1

2

J10

J/C

A

A BR

EC

A3
Compressor Lock Sensor

BR

DI–826

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

LEXUS RX300 (RM785E)

DTC

B1422/22 Compressor Lock Sensor Circuit

CIRCUIT DESCRIPTION

This sensor sends 4 pulses per engine revolution to the engine and ECT ECU.
If the number ratio of the compressor speed divided by the engine speed is smaller than a predetermined
value, the engine and ECT ECU turns the compressor OFF. And, the indicator flashes at about 1 second
intervals.

DTC No.

Detection Item

Trouble Area

B1422/22

All conditions below are detected for 3 secs. or more

(a) Engine speed : 450rpm or more

(b) Ratio between engine and compressor speed deviates 20%

or more in comparison to normal operation.

S Compressor.

S Compressor drive belt.

S Compressor lock sensor.

S Harness and connector between compressor and engine and

ECT ECU.

S Harness and connector between engine and ECT ECU and

A/C ECU (Combination meter ECU).

S Engine and ECT ECU.

S A/C ECU (Combination meter ECU).

WIRING DIAGRAM

DI3FY–03

I08339

LCKI

(+)

(–)

I05252

2

1

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–827

LEXUS RX300 (RM785E)

INSPECTION PROCEDURE

1

Check voltage between terminal LCKI of engine and ECT ECU and body ground.

CHECK:
(a)

Start engine.

(b)

Push AUTO SW.

(c)

Measure voltage between terminal LCKI of engine and
ECT ECU connector and body ground when A/C switch
is ON.

OK:

Voltage : 10 – 14 V

OK

Proceed to next circuit inspection shown on
problem symptoms table (See page DI–812).

NG

2

Check compressor lock sensor.

PREPARATION:
(a)

Jack up the vehicle.

(b)

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) : 990 – 1210 Ω

at 100

°C (212°F) : 1280 – 1550 Ω

NG

Replace compressor lock sensor.

OK

3

Check harness and connectors between engine and ECT ECU and compressor
lock sensor (See page IN–32).

NG

Repair or replace harness or connector.

OK

DI–828

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

LEXUS RX300 (RM785E)

4

Check harness and connectors between engine and ECT ECU and A/C ECU
(Combination meter ECU). (See page IN–32).

NG

Repair or replace harness or connector.

OK

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

I08340

Engine and ECT ECU

PRE

E10

2

R–Y*

1

EC1

16

G–R*

1

1

4

W–B

A4
Pressure Switch

J2

J/C

ED

A

G*

2

G*

2

*

1

: LHD

*

2

: RHD

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–829

LEXUS RX300 (RM785E)

DTC

B1423/23 Pressure Switch Circuit

CIRCUIT DESCRIPTION

The pressure switch sends the appropriate signals to the engine and ECT ECU when the A/C refrigerant
pressure drops too low or rises too high. When the engine and ECT ECU receives these signals, it outputs
signals via the engine and ECT ECU to switch OFF the compressor relay and turns the magnetic clutch OFF.

DTC No.

Detection Item

Trouble Area

B1423/23

S Open in pressure sensor circuit.

S Abnormal refrigerant pressure.
below 196 kPa (2.0 kgf/cm

2

, 31 psi)

over 3,140 kPa (32.0 kgf/cm

2

, 455 psi)

S Pressure switch.

S Harness or connector between pressure switch and engine

and ECT ECU.

S Refrigerant pipe line.

S Engine and ECT ECU.

WIRING DIAGRAM

DI3FZ–03