Lexus SC300 / Lexus SC400. Manual - part 24

Diag. Code 22

Compressor Lock Sensor Circuit

CIRCUIT DESCRIPTION

This sensor sends 4 pulses per engine revolution to the air conditioner control assembly.
If the number ratio of the compressor speed, divided by the engine speed is smaller that a predetermined
value, the air conditioner control assembly turns the compressor off. And, the indicator flashes at about
1 second intervals.

Code No.

Diag. Code Detecting Condition

Trouble area

22

All conditions below are detected for 3 secs.
or more. (a) Engine rpm: 450 rpm or more
(b) Ratio between engine and compressor
rpm deviates 20% or more in comparison to
normal operation.

Compressor

Compressor drive belt.

Compressor lock sensor.

Harness and connector between compressor
and A/C control assembly.

A/C control assembly.

DIAGNOSTIC CHART

Check compressor.

Check compressor lock sensor.

Check harness and connectors between air

conditioner control assembly and compres-
sor  sensor (See page

IN-27

).

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

AC-36

). However,

when Diag. code 22 is displayed, check

and replace air conditioner control assem-

bly.

Adjust drive belt tension or repair
compressor.

Replace compressor lock  sensor.

Repair or replace harness or
connector.

AC–54

–

AIR CONDITIONING SYSTEM

Troubleshooting

INSPECTION PROCEDURE

Check compressor

(1). Check compressor drive belt tension (See page 

AC-104

).

(2). Check if the compressor does not lock during with engine started and blower switch

and A/C switch ON.

Adjust drive belt tension or repair compressor.

Check compressor lock sensor.

Disconnect compressor lock sensor connector.

Measure resistance between terminals 1 and 2 of 
compressor lock sensor connector.

Resistance:

at 25

°

C (77

°

F) :   530 –650

at 100

°

C (212

°

F) :   670 –890

Replace  compressor lock sensor.

Check for open and short in harness and connectors between air conditioner
control assembly and compressor lock sensor (See page 

IN-27

).

Repair or replace harness or connector.

Proceed to next circuit inspection shown on
matrix chart (See page AC-36).However,
when Diag. code 22 is displayed, check and
replace air conditioner control assembly.

–

AIR CONDITIONING SYSTEM

Troubleshooting

AC–55

Diag. Code 23

Compressor Lock Sensor Circuit

CIRCUIT DESCRIPTION

The pressure switch sends the appropriate signals to the air conditioner control assembly when the air
conditioner refrigerant pressure drops too low or rises too high. When the air conditioner control assem-
bly receives these signals, it outputs signals via the Engine & ECT ECU to switch off the compressor
relay and turns the magnet clutch off.

Code No.

Diag. Code Detecting Condition

Trouble area

23

Open in pressure sensor circuit.

Abnormal refrigerant pressure.
below 206 kPa (2.1 kgf/cm

2

, 30 psi)

over 2,650 kPa (27 kgf/cm

2

, 385 psi)

Pressure switch.

Harness or connector between pressure switch
and ECU. Refrigerant pipe line.

 ECU.

DIAGNOSTIC CHART

Check voltage between terminals LP of  air

conditioner control assembly and body

ground.

Check pressure switch.

Check harness and connector between air

conditioner control assembly and pressure

switch and body ground
(See page 

IN-27

).

Check and replace air conditioner control 

assembly.

Proceed to next circuit inspection

shown on matrix chart (See page

AC-36

).

Replace pressure switch

Repair or replace harness or

connector.

AC–56

–

AIR CONDITIONING SYSTEM

Troubleshooting

9

Check  voltage between terminals LP of air conditioner control
assembly and body ground.

(1)

Install the manifold gauge set.

(See page 

AC-15

).

(2)

Turn ignition switch ON.

Check voltage between terminals LP of air conditioner
control assembly connector and body ground when the
air conditioner gas pressure is 
changed.

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

Low Pressure Cut Side

<Reference>

High pressure Cut Side

Proceed to next circuit inspection shown on
matrix chart (See page AC-36).

Check  pressure switch.

Disconnect pressure switch connector.
Check continuity between terminals 1 and 4 of pres-
sure switch when air conditioner gas pressure is
changed.

The continuity changes with gas pressure as
shown below.

Low Pressure Cut Side

<Reference>

High pressure Cut Side

Replace pressure switch

Check for open and short in harness and connector between air conditioner control
assembly and pressure switch, pressure switch and body ground (See page 

IN-27

).

Repair or replace harness or connector.

Check and replace air conditioner control
assembly.

INSPECTION PROCEDURE

–

AIR CONDITIONING SYSTEM

Troubleshooting

AC–57