Lexus NX: Open in Pressure Sensor Circuit / Abnormal Refrigerant Pressure (B1423)

Lexus NX Service Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System / Open in Pressure Sensor Circuit / Abnormal Refrigerant Pressure (B1423)

DESCRIPTION

This DTC is stored if refrigerant pressure on the high pressure side is extremely low (176 kPa (1.8 kgf/cm2, 26 psi) or less) or extremely high (3025 kPa (30.8 kgf/cm2, 439 psi) or more). The air conditioning tube and accessory assembly (air conditioner pressure sensor), which is installed on the pipe on the high pressure side 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

Note

B1423

Open in Pressure Sensor Circuit / Abnormal Refrigerant Pressure

  • Open or short in air conditioner pressure sensor circuit
  • Refrigerant pressure on high pressure side is extremely low (176 kPa [1.8 kgf/cm2, 26 psi] or less) or extremely high (3025 kPa [30.8 kgf/cm2, 439 psi] or more)
  • Air conditioning tube and accessory assembly (air conditioner pressure sensor)
  • Harness or connector
  • Air conditioning amplifier assembly
  • Cooler expansion valve (blocked, stuck)
  • Condenser assembly (blocked, deterioration of cooling capacity due to dirt)
  • Cooler dryer (moisture in the refrigerant cycle cannot be absorbed)
  • Cooling fan system (condenser assembly cannot be cooled down)
  • Air conditioning system (leaks, blocked)

-

-

HINT:

The air conditioning amplifier assembly stores the DTC of the respective malfunction if it has occurred for the period of time indicated in the brackets.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When the auxiliary battery is disconnected or the air conditioning amplifier assembly is replaced, be sure to perform servo motor initialization.

Click here

HINT:

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

PROCEDURE

1.

CHECK AIR CONDITIONER PRESSURE SENSOR (POWER SOURCE CIRCUIT)

(a) Disconnect the air conditioner pressure sensor connector.

*a

Front view of wire harness connector

(to Air Conditioner Pressure Sensor)

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

A18-3 (+) - A18-1 (-)

Power switch on (IG)

4.75 to 5.25 V

NG

GO TO STEP 4

OK

2.

CHECK AIR CONDITIONER PRESSURE SENSOR (SENSOR SIGNAL CIRCUIT)

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

Click here

*a

Component with harness connected

(Air Conditioning Amplifier Assembly)

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

I50-9 (PRE) - Body ground

Power switch on (IG)

A/C switch off

0.62 to 4.73 V

HINT:

If the measured voltage is not within the normal range, 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.

NG

GO TO STEP 11

OK

3.

CHECK AIR CONDITIONER PRESSURE SENSOR (SENSOR SIGNAL CIRCUIT)

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

Item

Condition

Vehicle Doors

Fully open

Temperature Setting

MAX COLD

Blower Speed

Hi

A/C Switch

On

R/F Switch

Recirculation

Interior Temperature

25 to 35°C (77 to 95°F)

NOTICE:

  • If refrigerant pressure on the high pressure side becomes extremely high during the inspection (if the voltage exceeds 4.8 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 problem symptom 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 ambient temperature sensor and the evaporator temperature sensor 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

Switch Condition

Specified Condition

I50-9 (PRE) - Body ground

Power switch on (IG)

A/C switch on

0.62 to 4.73 V

*a

Component with harness connected

(Air Conditioning Amplifier Assembly)

Result

Proceed to

OK (When troubleshooting according to the DTC)

A

OK (When troubleshooting according to Problem Symptoms Table)

B

NG

C

A

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

B

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

C

GO TO STEP 5

4.

CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - AIR CONDITIONING TUBE AND ACCESSORY ASSEMBLY [AIR CONDITIONER PRESSURE SENSOR])

(a) Disconnect the I50 air conditioning amplifier assembly connector.

(b) Disconnect the A18 air conditioning tube and accessory assembly (air conditioner pressure sensor) connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I50-10 (S5-3) - A18-3 (+)

Always

Below 1 Ω

I50-10 (S5-3) or A18-3 (+) - Body ground

Always

10 kΩ or higher

OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.

CHECK COOLING FAN SYSTEM

(a) Check that the cooling fan(s) operates normally.

Click here

NG

GO TO COOLING FAN SYSTEM

OK

6.

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 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 DTC.

NEXT

7.

CHECK FOR DTC

(a) Check for DTC when the following conditions are satisfied.

Item

Condition

Vehicle Doors

Fully open

Temperature Setting

MAX COLD

Blower Speed

Hi

A/C Switch

On

R/F Switch

Recirculation

Interior Temperature

25 to 35°C (77 to 95°F)

NOTICE:

If refrigerant pressure on the high pressure side becomes high, the DTC will be set. It is necessary to measure the voltage for a certain amount of time (approximately 10 minutes) because the DTC may be set 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 ambient temperature sensor and the evaporator temperature sensor 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 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 DTC. If the DTC is not output after this work, it indicates that the cooler dryer in the condenser 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 is not output

A

DTC B1423 is output

B

A

REPLACE COOLER CONDENSER ASSEMBLY

B

8.

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 expansion valve is either stuck or clogged.

NEXT

9.

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 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 DTC.

NEXT

10.

CHECK FOR DTC

(a) Check for DTC when the following conditions are satisfied.

Item

Condition

Vehicle Doors

Fully open

Temperature Setting

MAX COLD

Blower Speed

Hi

A/C Switch

On

R/F Switch

Recirculation

Interior Temperature

25 to 35°C (77 to 95°F)

NOTICE:

If refrigerant pressure on the high pressure side becomes high, the DTC will be set. It is necessary to measure the voltage for a certain amount of time (approximately 10 minutes) because the DTC may be set 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 ambient temperature sensor and the evaporator temperature sensor 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 expansion valve with a normal one, the condenser or pipes may be clogged due to dirt, dust or other foreign matter. In this case, clean or replace the condenser or pipes.

Result

Proceed to

DTC B1423 is not output

A

DTC B1423 is output

B

A

END (COOLER EXPANSION VALVE IS DEFECTIVE)

B

CLEAN OR REPLACE COOLER CONDENSER ASSEMBLY

11.

CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - AIR CONDITIONING TUBE AND ACCESSORY ASSEMBLY [AIR CONDITIONER PRESSURE SENSOR])

(a) Disconnect the I50 air conditioning amplifier assembly connector.

(b) Disconnect the A18 air conditioning tube and accessory assembly (air conditioner pressure sensor) connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I50-9 (PRE) - A18-2 (PR)

Always

Below 1 Ω

I50-9 (PRE) or A18-2 (PR) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

12.

CHECK 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 in it.

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.

Result

Proceed to

Vacuum can be maintained in the air conditioning system

A

Vacuum cannot be maintained in the air conditioning system

B

B

GO TO STEP 17

A

13.

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 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 DTC.

NEXT

14.

CHECK FOR DTC

(a) Check for DTC when the following conditions are satisfied.

Item

Condition

Vehicle Doors

Fully open

Temperature Setting

MAX COLD

Blower Speed

Hi

A/C Switch

On

R/F Switch

Recirculation

Interior Temperature

25 to 35°C (77 to 95°F)

NOTICE:

  • If refrigerant pressure on the high pressure side becomes high, the DTC will be set. It is necessary to measure the voltage for a certain amount of time (approximately 10 minutes) because the DTC may be set after the air conditioning operates for a while.
  • If the DTC was stored due 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 refrigerant when the level was insufficient. Therefore, identify and repair the area where refrigerant leaks from as necessary.

HINT:

When the outside air temperature is low (below -1.5°C [29.3°F]), the compressor stops due to operation of the ambient temperature sensor and the evaporator temperature sensor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment.

Result

Proceed to

DTC B1423 is not output

A

DTC B1423 is output

B

A

END

B

15.

CHECK AIR CONDITIONER PRESSURE SENSOR

(a) Install a manifold gauge set.

(b) Turn the power switch on (IG).

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

I50-9 (PRE) - I50-13 (SG-2)

Engine running

Air conditioning system operating

Refrigerant pressure: (below 3025 kPa [30.8 kgf/cm2, 439 psi] and higher than 176 kPa [1.8 kgf/cm2, 26 psi])

0.62 to 4.73 V

*a

Component with harness connected

(Air Conditioning Amplifier Assembly)

NG

REPLACE AIR CONDITIONING TUBE AND ACCESSORY ASSEMBLY (AIR CONDITIONER PRESSURE SENSOR)

OK

16.

CHECK FOR DTC

(a) Check for DTC when the following conditions are satisfied.

Item

Condition

Vehicle Doors

Fully open

Temperature Setting

MAX COLD

Blower Speed

Hi

A/C Switch

On

R/F Switch

Recirculation

Interior Temperature

25 to 35°C (77 to 95°F)

NOTICE:

  • If refrigerant pressure on the high pressure side becomes high, the DTC will be set. It is necessary to measure the voltage for a certain amount of time (approximately 10 minutes) because the DTC may be set after the air conditioning operates for a while.
  • If the DTC was stored due 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 refrigerant when the level was insufficient. Therefore, identify and repair the area where refrigerant leaks from as necessary.

HINT:

When the outside air temperature is low (below -1.5°C [29.3°F]), the compressor stops due to operation of the ambient temperature sensor and the evaporator temperature sensor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment.

Result

Proceed to

DTC B1423 is not output

A

DTC B1423 is output

B

A

END

B

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

17.

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

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