DTC B1474-4B: A/C Inverter Cooling/Heating Over Temperature [11/2021 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus NX 350h, 2024 Lexus NX 350h, 2023 Lexus NX 350h, and 2022 Lexus NX 350h. However, it is still accessible from the selected car via links, so may be relevant.

PERFORM ACTIVE TEST USING GTS

Perform the Active Test according to the display on the GTS.

Powertrain > Engine > Active Test

Tester Display	Measurement Item	Control Range	Restrict Condition
Control the Engine Cooling Fan Duty Ratio	Control the cooling fan	0 to 100%	Perform this test when vehicle is stopped.

Powertrain > Engine > Active Test

Tester Display
Control the Engine Cooling Fan Duty Ratio

Electric cooling fan operates smoothly.

Result

Proceed to
OK
NG

Result:

GO TO COOLING FAN SYSTEM. Refer to ON-VEHICLE INSPECTION [11/2021 - ]

Result:

See step 2

CHECK REFRIGERANT PRESSURE

Install a manifold gauge set.
Refer to ON-VEHICLE INSPECTION [11/2021 - ]

Prepare the vehicle according to the table below.

MEASUREMENT CONDITION:

Item	Condition
Doors	Fully open
A/C Switch	On
Recirculation/fresh Control Switch	Recirculation
Set Temperature	MAX COLD
Blower Speed	HI
Air Conditioning Air Inlet Temperature	25 to 35°C (77 to 95°F)

Read the manifold gauge pressure.

Standard Pressure

Low pressure side

150 to 250 kPa (1.5 to 2.5 kgf/cm² , 22 to 36 psi)

High pressure side

1370 to 1570 kPa (14 to 16 kgf/cm² , 199 to 228 psi)

Result

Proceed to
OK
NG

Result:

CHARGE REFRIGERANT. Refer to REPLACEMENT [11/2021 - ]

Result:

See step 3

CLEAR DTC

Clear the DTCs.

Body Electrical > Air Conditioner > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 4

CHECK FOR DTC

Set the vehicle condition when the DTCs are output.

Set the "Inspection Mode".
Refer to INSPECTION MODE PROCEDURE [11/2021 - ]

Prepare the vehicle according to the table below for 30 minutes or more.

Item	Condition
Blower Speed	HI
A/C Switch	On
Set Temperature	MAX COLD

Check for DTCs.

Body Electrical > Air Conditioner > Trouble Codes

NOTE:

If the engine keeps idling when the ambient temperature is high, the compressor with motor assembly may automatically stop to protect the inverter circuit, and DTC B1474-4B may be stored.

Result

Result	Proceed to
DTC B1474-4B is not output	A
DTC B1474-4B is output	B

Result:

USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [11/2021 - ]

Result:

REPLACE COMPRESSOR WITH MOTOR ASSEMBLY. Refer to REMOVAL [11/2021 - ]