Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: How To Proceed With Troubleshooting

CAUTION / NOTICE / HINT

PROCEDURE

1.	VEHICLE BROUGHT TO WORKSHOP

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2.	CUSTOMER PROBLEM ANALYSIS

What	Vehicle model, system name
When	Date, time, occurrence frequency
Where	Whether the problem occurs at a specific location.
Under what conditions?	Whether the doors were locked or unlocked, whether the engine switch was on, whether the engine was running.
How did it happen?	Problem symptoms

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3.

PRE-CHECK

(a) Measure the battery voltage.

Standard Voltage:

11 to 14 V

If the voltage is below 11 V, recharge or replace the battery before proceeding to the next step.

(b) Check the fuses and relays.

(c) Check the connector connections and terminals to make sure that there are no abnormalities such as loose connections, deformation, etc.

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4.	TURN ENGINE SWITCH ON (IG)

NOTICE:

When using the Techstream with the engine switch off, connect the Techstream to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the Techstream and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Access. While using the Techstream, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the Techstream and the vehicle.

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5.	INSPECT COMMUNICATION FUNCTION OF CAN COMMUNICATION SYSTEM*

(a) Using the Techstream, check for CAN communication system DTCs.

Click here

Result	Proceed to
CAN DTCs are not output	A
CAN DTCs are output	B

B

GO TO CAN COMMUNICATION SYSTEM

A

6.	INSPECT COMMUNICATION FUNCTION OF LIN COMMUNICATION SYSTEM*

(a) Using the Techstream, check for LIN communication system DTCs.

Click here

Result	Proceed to
LIN DTCs are not output	A
LIN DTCs are output	B

B

GO TO LIN COMMUNICATION SYSTEM

A

7.	CHECK FOR DTC*

(a) Check for DTCs and make a note of any codes that are output.

Body Electrical > Smart Access > Trouble Codes Powertrain > Engine > Trouble Codes

(b) Based on the DTCs output above, proceed to each diagnostic procedure.

Result	Proceed to
DTCs are not output	A
SFI system DTCs are output	B
Steering lock system DTCs are output	C
Immobiliser system DTCs are output	D

B

GO TO DIAGNOSTIC TROUBLE CODE CHART

C

GO TO DIAGNOSTIC TROUBLE CODE CHART

D

GO TO DIAGNOSTIC TROUBLE CODE CHART

A

8.	PROBLEM SYMPTOMS TABLE

(a) Refer to Problem Symptoms Table.

Click here

Result	Proceed to
Fault is not listed in Problem Symptoms Table	A
Fault is listed in Problem Symptoms Table	B

B

GO TO STEP 10

A

9.	OVERALL ANALYSIS AND TROUBLESHOOTING*

(a) Data List / Active Test

Click here

(b) Terminals of ECU

Click here

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10.	REPAIR OR REPLACE

HINT:

When replacing the Certification ECU (smart key ECU assembly), ID code box (immobiliser code ECU), steering lock ECU (steering lock actuator or upper bracket assembly), main body ECU (multiplex network body ECU), ECM or electrical key transmitter sub-assembly, refer to Registration.

Click here

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11.	CHECK FOR DTC*

(a) Clear the DTCs.

Body Electrical > Smart Access > Clear DTCs Powertrain > Engine > Clear DTCs

(b) Check for DTCs.

Body Electrical > Smart Access > Trouble Codes Powertrain > Engine > Trouble Codes

HINT:

Before checking for DTCs, perform the "DTC Output Confirmation Operation" of each diagnostic procedure.

Result	Proceed to
DTCs are not output	A
Immobiliser system DTCs are output	B

A

END

B

GO TO DIAGNOSTIC TROUBLE CODE CHART