Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Diagnosis System

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Immobiliser System / Diagnosis System

DIAGNOSIS SYSTEM

DESCRIPTION

(a) The certification ECU (smart key ECU assembly) and ECM control the vehicle immobiliser system functions. Immobiliser system data and Diagnostic Trouble Codes (DTCs) can be read through the vehicle Data Link Connector 3 (DLC3).

In some cases, a malfunction may be occurring in the immobiliser system even though the security indicator light is not illuminated.

When the system seems to be malfunctioning, use the Techstream to check for malfunctions and perform repairs.

CHECK DLC3

(a) Check the DLC3.

Click here

INSPECT BATTERY VOLTAGE

(a) Measure the battery voltage.

Standard Voltage:

11 to 14 V

If the voltage is below 11 V, recharge or replace the battery.

START FUNCTION PROBLEM SYMPTOMS

Symptom

Suspected Area

Component Malfunction

Possible Output DTCs

Related Data List Item

Engine cannot be started*1

Certification ECU (smart key ECU assembly)

Open or short circuit inside ECU
  • B278A
  • B279986
  • B279A12
  • #Codes
  • Immobilizer when IG=ON
  • Immobiliser
  • Master Key
  • Sub Key
  • BCC Malfunction
  • Abnormal Status
  • Different Encrypt Code
  • Different Serial Number
  • Frame Error
  • Response
  • Wireless Starter Com ID
  • Wireless C Code
  • Engine Start Condition
  • ID-BOX Sleep Condition
  • ID-BOX Start Condition
  • Engine Start Request
  • 3bit Code Request
  • S Code Check
  • L Code Check
  • Unlock Request Receive
  • Lock Request Receive
  • S Code Check (Past)
  • L Code Check (Past)
  • EFI Code Receive
  • EFI Communication

Engine cannot be started*1

ID code box (immobiliser code ECU)

Open or short circuit inside ECU
  • B2790
  • B279986
  • B279A12
  • Immobilizer when IG=ON
  • Immobiliser
  • Master Key
  • Sub Key
  • BCC Malfunction
  • Abnormal Status
  • Different Encrypt Code
  • Different Serial Number
  • Frame Error
  • Response
  • ID-BOX Sleep Condition
  • ID-BOX Start Condition
  • Engine Start Request
  • 3bit Code Request
  • S Code Check
  • L Code Check
  • S Code Check (Past)
  • L Code Check (Past)
  • EFI Code Receive
  • EFI Communication

ECM

Open or short circuit inside ECU
  • B279986
  • B279A12
  • B279C95

EFI Code Receive

SFI system

ECM incompatible with installed immobiliser system

B279C95
  • Engine Start Condition
  • EFI Code Receive

Power source mode cannot be changed*1

Engine switch

Open or short circuit inside switch

B278A
  • Unlock Request Receive
  • Lock Request Receive

Certification ECU (smart key ECU assembly)

Open or short circuit inside ECU
  • B2271
  • B2274
  • Immobilizer when IG=ON
  • Immobiliser

Steering lock lock/unlock not possible*2

Steering lock ECU (steering lock actuator or upper bracket assembly)
  • Open or short circuit inside ECU
  • Actuator stuck
  • B2781
  • B2782
  • B2788
  • Unlock Request Receive
  • Lock Request Receive
  • *1: Refer to Problem Symptoms Table for Smart Access System with Push-button Start (for Start Function).

    Click here

  • *2: Refer to Problem Symptoms Table for Steering Lock System.

    Click here

    Data List / Active Test
    DATA LIST / ACTIVE TEST DATA LIST NOTICE: In the table below, the values listed under "Normal Condition" are reference values. Do not depend solely on these reference values when deciding whether a pa ...

    Dtc Check / Clear
    DTC CHECK / CLEAR 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 ...

    Other materials:

    Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual > Lighting System (w/o Automatic Headlight Beam Level Control System): Parts Location
    PARTS LOCATION ILLUSTRATION *A w/ Automatic High Beam System - - *1 HEADLIGHT ASSEMBLY LH - HEADLIGHT UNIT LH *2 HEADLIGHT ASSEMBLY RH - HEADLIGHT UNIT RH *3 SIDE TURN SIGNAL LIGHT ASSEMBLY LH *4 SIDE TURN SIGNAL LIGHT ASSEMBLY RH *5 FRONT DOOR OUTSIDE HANDLE ASSE ...

    Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual > Dynamic Torque Control Awd System: Freeze Frame Data
    FREEZE FRAME DATA FREEZE FRAME DATA (a) When a DTC is stored, the 4WD ECU assembly stores the current vehicle state as Freeze Frame Data. HINT: When Freeze Frame Data is stored along with the DTC, the Freeze Frame Data is not updated until it is cleared. "Number of IG ON" is not stored as Freez ...

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

    © 2025 Copyright www.lexusrx.net
    0.0109