L-SB-0035-22

August 15, 2022

ECU Security Key Writing
Service
Category

Power Source/Network

Section

Networking

Market USA and Mexico

Applicability
YEAR(S)

MODEL(S)

2022

LS500, LS500H, LX600,
NX250, NX350, NX350H,
NX450H+

ADDITIONAL INFORMATION

Introduction

When certain vehicle ECUs are replaced, the ECU security key must be written in order for that
ECU to communicate on the vehicle network. The Techstream Software Health Check Results
screen has been enhanced to help identify if a replacement ECU requires an ECU security key.
Follow the procedures in this bulletin to write the ECU security key to the replacement ECU.
Figure 1.

Warranty Information
OP CODE

DESCRIPTION

TIME

OFP

T1

T2

N/A

Not Applicable to Warranty

–

–

–

–

© 2022 Lexus, a division of Toyota Motor Sales, USA

L-SB-0035-22

August 15, 2022

Page 2 of 9

ECU Security Key Writing
Required Tools & Equipment
REQUIRED EQUIPMENT

SUPPLIER

Techstream ADVI*

PART NUMBER

QTY

TSADVUNIT

Techstream 2.0

TS2UNIT
ADE

1

Techstream Lite

TSLITEPDLR01

Techstream Lite (Green Cable)

TSLP2DLR01

*Essential SST.

NOTE
 Only ONE of the Techstream units listed above is required.
 Software version 17.10.012 or later is required.
 Additional Techstream units may be ordered by calling Approved Dealer Equipment (ADE)
at 1-800-368-6787 (USA) or 01-55-50103041 (Mexico).

Procedures





Confirm ECU Security Key Writing Requirement ........................................................................ 3


Health Check ....................................................................................................................... 3



ECU Security Key Button ..................................................................................................... 4

ECU Security Key Writing Process ............................................................................................ 5

© 2022 Lexus, a division of Toyota Motor Sales, USA

L-SB-0035-22

August 15, 2022

Page 3 of 9

ECU Security Key Writing
Confirm ECU Security Key Writing Requirement

After ECU replacement, it is important to confirm if ECU security key writing is necessary. There
are two methods available to confirm if the ECU security key writing function is required within the
Techstream software: performing a Health Check and using the ECU Security Key button.
Health Check

Performing a Health Check will confirm if ECU security key writing is needed. The Techstream
Health Check Results screen has been enhanced to include an ECU security key indicator. The
ECU security key indicator will display “Necessary” when an ECU security key needs to be
written and “-” when ECU security key writing is NOT required.
Figure 2.

© 2022 Lexus, a division of Toyota Motor Sales, USA

L-SB-0035-22

August 15, 2022

Page 4 of 9

ECU Security Key Writing
Confirm ECU Security Key Writing Requirement (continued)
ECU Security Key Button

Selecting the ECU Security Key Button is another method to confirm if ECU security key writing is
required. From the System Select screen the ECU Security Key button is located on the left-hand
side of the function menu.
NOTE
Selecting this option can allow ECU security key writing even if it is not required. If the ECU security key
does NOT need to be written, a message will appear stating “ECU Security Key is already registered.”
Figure 3.

© 2022 Lexus, a division of Toyota Motor Sales, USA

L-SB-0035-22

August 15, 2022

Page 5 of 9

ECU Security Key Writing
ECU Security Key Writing Process
NOTE
The process outlined in this section will use the Health Check Result screen to confirm if ECU security key
writing is required.

1. Connect Techstream to the vehicle and press Next.
NOTE
In some instances, automatic vehicle detection may not be available due to specific ECU
replacement. If the vehicle information does NOT automatically populate, manually select the
appropriate vehicle information.

Figure 4.

© 2022 Lexus, a division of Toyota Motor Sales, USA

L-SB-0035-22

August 15, 2022

Page 6 of 9

ECU Security Key Writing
ECU Security Key Writing Process (continued)

2. Perform a Health Check.
If the ECU Security Key indicator in the upper-right corner of the Health Check screen
displays “Necessary,” press the ECU key button, located on the bottom of the screen.
Figure 5.

© 2022 Lexus, a division of Toyota Motor Sales, USA

L-SB-0035-22

August 15, 2022

Page 7 of 9

ECU Security Key Writing
ECU Security Key Writing Process (continued)

3. Select Next.
Figure 6.

4. Techstream will read the vehicle information and open TIS to download the ECU security key.
Input your TIS login credentials and select Login.
Figure 7.

© 2022 Lexus, a division of Toyota Motor Sales, USA

L-SB-0035-22

August 15, 2022

Page 8 of 9

ECU Security Key Writing
ECU Security Key Writing Process (continued)

5. Select Send.
Figure 8.

6. After pressing Send, TIS will automatically send the ECU security key to Techstream. Return
to Techstream and wait for the writing process to complete.
Figure 9.

© 2022 Lexus, a division of Toyota Motor Sales, USA

L-SB-0035-22

August 15, 2022

Page 9 of 9

ECU Security Key Writing
ECU Security Key Writing Process (continued)

7. Cycle the ignition to IG-OFF, then IG-ON. Select Next.
Figure 10.

8. Select OK.
Figure 11.

9. Confirm the ECU security key has been properly written by performing a Health Check and
confirming the ECU security key indicator shows “-”; then, clear ALL DTCs.
Figure 12.

NOTE
The ECU security key indicator will show “Necessary” if the security key was NOT written properly. If
NOT written properly return to step 2.

© 2022 Lexus, a division of Toyota Motor Sales, USA