Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Ignition Hold Monitor Malfunction (B2271)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Access System With Push-button Start (for Start Function) / Ignition Hold Monitor Malfunction (B2271)

DESCRIPTION

This DTC is stored when a malfunction in the IG circuit or IG hold circuit of the certification ECU (smart key ECU assembly) is detected.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B2271

Ignition Hold Monitor Malfunction

When either of the following conditions is met (1-trip detection logic*1):

  • The IG circuit of the certification ECU (smart key ECU assembly) is malfunctioning.*2
  • The IG hold circuit of the certification ECU (smart key ECU assembly) is malfunctioning.*3
  • AM2 fuse
  • Certification ECU (smart key ECU assembly)
  • Wire harness or connector
  • Turn the engine switch on (IG).
  • *1: Only detected while a malfunction is present and the engine switch is on (IG).
  • *2: The IG circuit and IG hold circuit activate the IG relay.
  • *3: After the IG circuit turns on, even if the certification ECU (smart key ECU assembly) malfunctions, the IG hold circuit will maintain the power source mode in on (IG).
Vehicle Condition and Fail-safe Function when Malfunction Detected

Vehicle Condition when Malfunction Detected

Fail-safe Function when Malfunction Detected

The engine switch cannot be turned on (IG) (the engine cannot be started).

The power source mode cannot be changed to on (IG).
Related Data List and Active Test Items

DTC No.

Data List and Active Test

B2271
Power Source Control
  • IG Relay Monitor (Inside)
  • Latch Circuit
Starting Control
  • Ignition

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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.
  • The smart access system with push-button start (for Start Function) uses the LIN communication system and CAN communication system. Inspect the communication function by following How to Proceed with Troubleshooting. Troubleshoot the smart access system with push-button start (for Start Function) after confirming that the communication systems are functioning properly.

    Click here

  • Inspect the fuses of circuits related to this system before performing the following procedure.
  • Before replacing the certification ECU (smart key ECU assembly), refer to smart access system with push-button start (for Start Function) Precaution.

    Click here

  • After repair, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

HINT:

When the cable is disconnected and reconnected to the negative (-) battery terminal, the power source mode returns to the state it was in before the cable was disconnected.

PROCEDURE

1.

CHECK HARNESS AND CONNECTOR (POWER SOURCE)

(a) Disconnect the J41 certification ECU (smart key ECU assembly) connector.

*a

Front view of wire harness connector

(to Certification ECU (Smart Key ECU Assembly))

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

J41-4 (+B) - Body ground

Always

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR IN CIRCUIT CONNECTED TO POWER SOURCE
OK

2.

CHECK HARNESS AND CONNECTOR (GROUND)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J41-18 (E) - Body ground

Always

Below 1 Ω

*a

Front view of wire harness connector

(to Certification ECU (Smart Key ECU Assembly))
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

3.

CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Reconnect the J41 certification ECU (smart key ECU assembly) connector.

*a

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

J41-17 (IG1D) - Body ground

Engine switch on (ACC) → Engine switch on (IG)

1 V or less → 9 V or higher
OK

END (TEMPORARY CONNECTION FAILURE IS SUSPECTED)

NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

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