Lexus NX: No Response from ID BOX (B2789)

DESCRIPTION

This DTC is stored when LIN communication between the certification ECU (smart key ECU assembly) and ID code box (immobiliser code ECU) stops for 10 seconds or more.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B2789

No Response from ID BOX

No communication between the certification ECU and ID code box for 10 seconds or more.

  • ID code box (immobiliser code ECU)
  • Certification ECU (smart key ECU assembly)
  • Harness or connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When using the Techstream with the power switch off to troubleshoot:

    Connect the Techstream to the vehicle, and turn a courtesy light switch on and off at 1.5 second intervals until communication between the Techstream and vehicle begins.

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.
  • Before replacing the certification ECU (smart key ECU assembly) or immobiliser code ECU, refer to the immobiliser system.

HINT:

When the communication between the ID code box (immobiliser code ECU) and certification ECU (smart key ECU assembly) stops, DTC B2785 is also stored.

PROCEDURE

1.

CLEAR DTC

(a) Clear the DTCs.

Click here

Body Electrical > Smart Access > Clear DTCs
NEXT

2.

CHECK FOR DTC

(a) Check for DTCs.

Click here

Body Electrical > Smart Access > Trouble Codes
DTC B2789 is not output

USE SIMULATION METHOD TO CHECK

DTC B2789 is output

3.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU [SMART KEY ECU ASSEMBLY] - ID CODE BOX [IMMOBILISER CODE ECU])

(a) Disconnect the I53 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the I26 ID code box (immobiliser code ECU) connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I53-6 (LIN) - I26-2 (LIN1)

Always

Below 1 Ω

I53-6 (LIN) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.

CHECK HARNESS AND CONNECTOR (ID CODE BOX [IMMOBILISER CODE ECU] - BATTERY AND BODY GROUND)

(a) Disconnect the ID code box (immobiliser code ECU) connector.

*a

Front view of wire harness connector

(to ID Code Box [Immobiliser Code ECU])

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I26-5 (GND) - Body ground

Always

Below 1 Ω

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

I26-1 (+B) - Body ground

Power switch off

11 to 14 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

5.

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Temporarily replace the certification ECU (smart key ECU assembly) with a new one.

Click here

(b) Clear the DTCs.

Click here

Body Electrical > Smart Access > Clear DTCs
NEXT

6.

CHECK FOR DTC

(a) Check for DTCs.

Click here

Body Electrical > Smart Access > Trouble Codes
DTC B2789 is not output

END (CERTIFICATION ECU [SMART KEY ECU ASSEMBLY] IS DEFECTIVE)

DTC B2789 is output

REPLACE ID CODE BOX (IMMOBILISER CODE ECU)

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