Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Pressure Sensor Circuit (B1423/23)

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System / Pressure Sensor Circuit (B1423/23)

DESCRIPTION

This DTC is stored if refrigerant pressure on the high pressure side is extremely low (196 kPa (2.0 kgf/cm2, 28 psi) or less) or extremely high (2812 kPa (28.7 kgf/cm2, 408 psi) or more). The air conditioner pressure sensor, which is installed to the high pressure side pipe to detect refrigerant pressure, sends a refrigerant pressure signal to the air conditioning amplifier assembly. The air conditioning amplifier assembly converts this signal to a pressure value according to the sensor characteristics and uses it to control the compressor.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

B1423/23

Pressure Sensor Circuit
  • Open or short in air conditioner pressure sensor circuit
  • Refrigerant pressure on high pressure side is extremely low (196 kPa (2.0 kgf/cm2, 28 psi) or less) or extremely high (2812 kPa (28.7 kgf/cm2, 408 psi) or more)
  • Air conditioner pressure sensor
  • Harness or connector between air conditioner pressure sensor and air conditioning amplifier assembly
  • Air conditioning amplifier assembly
  • Cooler expansion valve (blocked, stuck)
  • Cooler condenser assembly (blocked, deterioration of cooling capacity due to dirt)
  • Cooler dryer (moisture in the refrigerant cycle cannot be absorbed)
  • Cooling fan system (cooler condenser assembly cannot be cooled down)
  • Air conditioning system (leaks, blocked)

-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

If DTC B1423/23 and B14B8 are output at the same time, troubleshoot for DTC B1423/23 first.

PROCEDURE

1.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the A9 air conditioner pressure sensor connector.

(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Condition

Specified Condition

A9-3 (+) - A9-1 (-)

Engine switch on (IG)

4.75 to 5.25 V
NG

GO TO STEP 16

OK

2.

INSPECT AIR CONDITIONER PRESSURE SENSOR (SENSOR SIGNAL CIRCUIT)

(a) Reconnect the A9 air conditioner pressure sensor connector.

(b) Remove the air conditioning amplifier assembly with the connectors still connected.

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Condition

Specified Condition

J42-24 (PRE) - Body ground

Engine switch on (IG)

(A/C switch: Off)

0.74 to 4.61 V

HINT:

If the result is not as specified, there may be a malfunction in the air conditioning amplifier assembly, air conditioner pressure sensor, or wire harness. It is also possible that the amount of refrigerant may not be appropriate.

*a

Component with harness connected

(Air Conditioning Amplifier Assembly)
NG

GO TO STEP 10

OK

3.

INSPECT AIR CONDITIONER PRESSURE SENSOR (SENSOR SIGNAL CIRCUIT)

(a) Measure the voltage when the following conditions are met.

Measurement Condition:

Item

Condition

Vehicle doors

Fully open

Temperature setting

MAX COLD

Blower speed

HI

A/C switch

On

Recirculation/fresh switch

RECIRCULATION

Interior temperature

25 to 35°C (77 to 95°F)

Engine speed

2000 rpm

NOTICE:

  • If refrigerant pressure on the high pressure side becomes extremely high during the inspection (if the voltage exceeds 4.61 V), the fail-safe function stops compressor operation. Therefore, measure the voltage before the fail-safe operation.
  • It is necessary to measure the voltage for a certain amount of time (approximately 10 minutes) because the malfunction may recur after a while.

HINT:

When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to operation of the cooler (ambient temp. sensor) thermistor and the No. 1 cooler thermistor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment.

(1) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Condition

Specified Condition

J42-24 (PRE) - Body ground

Engine switch on (IG)

(A/C switch: On)

0.74 to 4.61 V

Result

Proceed to

OK (When troubleshooting according to DTC)

A

OK (When troubleshooting according to Problem Symptoms Table)

B

NG

C

*a

Component with harness connected

(Air Conditioning Amplifier Assembly)
A

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

B

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

C

4.

INSPECT COOLING FAN SYSTEM

(a) Check if the cooling fan operates normally.

Click here

NG

GO TO COOLING FAN SYSTEM

OK

5.

CHARGE SYSTEM WITH REFRIGERANT

(a) Use a refrigerant recovery unit to recover refrigerant.

(b) Evacuate the air conditioning system.

(c) Add an appropriate amount of refrigerant.

Click here

HINT:

If refrigerant is added and the system has not been properly evacuated (insufficient vacuum time), moisture in the air remaining in the system will freeze in the cooler expansion valve, blocking the flow on the high pressure side. Therefore, in order to confirm the problem, recover the refrigerant and properly evacuate the system. Add an appropriate amount of refrigerant, and check for the DTC.

NEXT

6.

RECHECK FOR DTC

(a) Recheck for the DTC when the following conditions are met.

Measurement Condition:

Item

Condition

Vehicle doors

Fully open

Temperature setting

MAX COLD

Blower speed

HI

A/C switch

On

Recirculation/fresh switch

RECIRCULATION

Interior temperature

25 to 35°C (77 to 95°F)

Engine speed

2000 rpm
Body Electrical > Air Conditioner > Trouble Codes

NOTICE:

If refrigerant pressure on the high pressure side becomes high, the DTC will be stored. It is necessary to operate the air conditioning system for a certain amount of time (approximately 10 minutes) because the DTC may be stored after the air conditioning operates for a while.

HINT:

  • When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to operation of the cooler (ambient temp. sensor) thermistor and the No. 1 cooler thermistor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment.
  • If refrigerant is added and the system has not been properly evacuated (insufficient vacuum time), moisture in the air remaining in the system will freeze in the cooler expansion valve, blocking the flow on the high pressure side. Therefore, in order to confirm the problem, recover the refrigerant and properly evacuate the system. Add an appropriate amount of refrigerant, and check for the DTC. If the DTC is not output after this work, it indicates that the cooler dryer in the cooler condenser assembly is not able to absorb moisture in the refrigerant cycle. It is necessary to replace the cooler dryer in order to complete the repair.

Result

Proceed to

DTC B1423/23 is output

A

DTC B1423/23 is not output

B
B

REPLACE COOLER CONDENSER ASSEMBLY

A

7.

REPLACE COOLER EXPANSION VALVE

(a) Replace the cooler expansion valve with a new one.

Click here

HINT:

Replace the cooler expansion valve with a new one because the cooler expansion valve is either stuck or clogged.

NEXT

8.

CHARGE SYSTEM WITH REFRIGERANT

(a) Use a refrigerant recovery unit to recover refrigerant.

(b) Evacuate the air conditioning system.

(c) Add an appropriate amount of refrigerant.

Click here

HINT:

If refrigerant is added and the system has not been properly evacuated (insufficient vacuum time), moisture in the air remaining in the system will freeze in the cooler expansion valve, blocking the flow on the high pressure side. Therefore, in order to confirm the problem, recover the refrigerant and properly evacuate the system. Add an appropriate amount of refrigerant, and check for the DTC.

NEXT

9.

RECHECK FOR DTC

(a) Recheck for the DTC when the following conditions are met.

Measurement Condition:

Item

Condition

Vehicle doors

Fully open

Temperature setting

MAX COLD

Blower speed

HI

A/C switch

On

Recirculation/fresh switch

RECIRCULATION

Interior temperature

25 to 35°C (77 to 95°F)

Engine speed

2000 rpm
Body Electrical > Air Conditioner > Trouble Codes

NOTICE:

If refrigerant pressure on the high pressure side becomes high, the DTC will be stored. It is necessary to operate the air conditioning system for a certain amount of time (approximately 10 minutes) because the DTC may be stored after the air conditioning operates for a while.

HINT:

  • When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to operation of the cooler (ambient temp. sensor) thermistor and the No. 1 cooler thermistor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment.
  • If refrigerant pressure is not normal after replacing the cooler expansion valve with a new or known good one, the cooler condenser assembly or pipes may be clogged due to dirt, dust or other foreign matter. In this case, clean or replace the cooler condenser assembly or pipes.

Result

Proceed to

DTC B1423/23 is not output

A

DTC B1423/23 is output

B
A

END
B

CLEAN OR REPLACE COOLER CONDENSER ASSEMBLY OR PIPE

10.

CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - AIR CONDITIONER PRESSURE SENSOR)

(a) Disconnect the A9 air conditioner pressure sensor connector.

(b) Disconnect the J42 air conditioning amplifier assembly connector.

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

A9-2 (PR) - J42-24 (PRE)

Always

Below 1 Ω

J42-24 (PRE) or A9-2 (PR) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

11.

INSPECT FOR AIR CONDITIONING SYSTEM LEAK

(a) Install a manifold gauge set.

(b) Recover the refrigerant from the air conditioning system using a refrigerant recovery unit.

(c) Evacuate the air conditioning system and check that vacuum can be maintained.

OK:

Vacuum can be maintained in the air conditioning system.

HINT:

If vacuum cannot be maintained in the air conditioning system, refrigerant may be leaking from it. In this case, it is necessary to repair or replace the leaking part of the air conditioning system.

NG

GO TO STEP 15

OK

12.

CHARGE SYSTEM WITH REFRIGERANT

(a) Use a refrigerant recovery unit to recover refrigerant.

(b) Evacuate the air conditioning system.

(c) Add an appropriate amount of refrigerant.

Click here

HINT:

If refrigerant is added and the system has not been properly evacuated (insufficient vacuum time), moisture in the air remaining in the system will freeze in the cooler expansion valve, blocking the flow on the high pressure side. Therefore, in order to confirm the problem, recover the refrigerant and properly evacuate the system. Add an appropriate amount of refrigerant, and check for the DTC.

NEXT

13.

RECHECK FOR DTC

(a) Recheck for the DTC when the following conditions are met.

Measurement Condition:

Item

Condition

Vehicle doors

Fully open

Temperature setting

MAX COLD

Blower speed

HI

A/C switch

On

Recirculation/fresh switch

RECIRCULATION

Interior temperature

25 to 35°C (77 to 95°F)

Engine speed

2000 rpm
Body Electrical > Air Conditioner > Trouble Codes

NOTICE:

If refrigerant pressure on the high pressure side becomes high, the DTC will be stored. It is necessary to operate the air conditioning system for a certain amount of time (approximately 10 minutes) because the DTC may be stored after the air conditioning operates for a while.

HINT:

When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to operation of the cooler (ambient temp. sensor) thermistor and the No. 1 cooler thermistor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment.

Result

Proceed to

DTC B1423/23 is output

A

DTC B1423/23 is not output

B

NOTICE:

If the DTC was stored to an insufficient or excessive amount of refrigerant, the problem may have been solved after performing the previous step. However, the root cause of insufficient refrigerant may be refrigerant leaks. The root cause of excessive refrigerant may be adding too much refrigerant when the level was insufficient. Therefore, identify and repair the area where refrigerant leaks from as necessary.

B

END
A

14.

INSPECT AIR CONDITIONER PRESSURE SENSOR

(a) Install a manifold gauge set.

(b) Reconnect the A9 air conditioner pressure sensor connector.

(c) Turn the engine switch on (IG).

(d) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Condition

Specified Condition

J42-24 (PRE) - J42-3 (SG-4)

Refrigerant pressure: Normal pressure (less than 2812 kPa (28.7 kgf/cm2, 408 psi) and more than 196 kPa (2.0 kgf/cm2, 28 psi))

0.74 to 4.61 V

*a

Component with harness connected

(Air Conditioning Amplifier Assembly)
OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPLACE AIR CONDITIONER PRESSURE SENSOR

15.

REPAIR AIR CONDITIONING SYSTEM LEAK

(a) Identify the area where refrigerant leaks from.

Click here

(b) Repair the identified area of the air conditioning system.

(c) Evacuate the air conditioning system.

NEXT

CHARGE SYSTEM WITH REFRIGERANT

16.

CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - AIR CONDITIONER PRESSURE SENSOR)

(a) Disconnect the J42 air conditioning amplifier assembly connector.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

A9-3 (+) - J42-6 (S5-3)

Always

Below 1 Ω

J42-6 (S5-3) or A9-3 (+) - Body ground

Always

10 kΩ or higher
OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
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