NHTSA ID Number: 11014191
Manufacturer Communication Number: L-SB-0035-22 Rev2
TSB/Document Date: 2025-02-12
Summary
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 GTS+ Software Health Check Results screen has been enhanced to help identify if a replacement ECU requires an ECU Security Key.
L-SB-0035-22
Rev2
August 15, 2022
ECU Security Key Writing
Service
Category
Power Source/Network
Section
Networking
Market USA and Mexico
Applicability
YEAR(S)
MODEL(S)
2024 - 2025
GX550, RZ300E, TX350,
TX500H, TX550H+
2023 - 2025
LS500, LS500H, LX600,
NX250, NX350, NX350H,
NX450H+, RX350, RX350H,
RX450H+, RX500H,
RZ450E
2025
UX300H
ADDITIONAL INFORMATION
REVISION NOTICE
January 23, 2025 Rev2:
Applicability has been updated to include 2024 – 2025 model year GX 550 vehicles and
2025 model year LS 500, LS 500h, LX 600, NX 250, NX 350, NX 350h, NX 450h+, RX 350, RX 350h,
RX 450h+, RX 500h, RZ 300e, RZ 450e, TX 350, TX 500h, TX 550h+, and UX 300h vehicles.
April 11, 2024 Rev1:
Applicability has been updated to include 2023 – 2024 model year LS 500, LS 500h, LX 600,
NX 250, NX 350, NX 350h, NX 450h+, RX 350, RX 350h, RX 450h+, RX 500h, and RZ 450e and
2024 model year RZ 300e, TX 350, TX 500h, and TX 550h+ vehicles.
The entire bulletin has been updated to represent GTS+ Software.
Any previous printed versions of this bulletin should be discarded.
© 2025 Lexus
, a division of Toyota Motor Sales, USA
Page 1 of 11
L-SB-0035-22
Rev2
August 15, 2022
Page 2 of 11
ECU Security Key Writing
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 GTS+ 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
For USA and Mexico Markets
OP CODE
DESCRIPTION
TIME
OFP
T1
T2
N/A
Not Applicable to Warranty
–
–
–
–
© 2025 Lexus, a division of Toyota Motor Sales, USA
L-SB-0035-22
Rev2
August 15, 2022
Page 3 of 11
ECU Security Key Writing
Required Tools & Equipment
REQUIRED EQUIPMENT
SUPPLIER
PART NUMBER
Techstream ADVi*
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 2024.04.004.02 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) or by visiting TIS – Diagnostics –
Tools & Equipment – Techstream Order Portal.
SPECIAL SERVICE TOOLS (SST)
PART NUMBER
QTY
Battery Diagnostic Tool*
DCA-8000P T
1
*Essential SST.
NOTE
Additional SSTs may be ordered by calling 1-800-368-6787 (USA) or 01-800-504-5330 (Mexico) or by
visiting Home – Service Resources – Lexus Special Service Tools (SSTs).
Procedures
Confirm ECU Security Key Writing Requirement ........................................................................ 4
Health Check......................................................................................................................... 4
ECU Security Key Button ...................................................................................................... 5
ECU Security Key Writing Process ............................................................................................. 6
© 2025 Lexus, a division of Toyota Motor Sales, USA
L-SB-0035-22
Rev2
August 15, 2022
Page 4 of 11
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 GTS+ 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 GTS+ 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.
© 2025 Lexus, a division of Toyota Motor Sales, USA
L-SB-0035-22
Rev2
August 15, 2022
Page 5 of 11
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 Main Menu screen, select the ECU Security Key button.
Figure 3.
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 written.”
Figure 4.
© 2025 Lexus, a division of Toyota Motor Sales, USA
L-SB-0035-22
Rev2
August 15, 2022
Page 6 of 11
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 GTS+ to the vehicle and press the arrow button to go to the next step.
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 5.
© 2025 Lexus, a division of Toyota Motor Sales, USA
L-SB-0035-22
Rev2
August 15, 2022
Page 7 of 11
ECU Security Key Writing
ECU Security Key Writing Process (continued)
2. Perform a Health Check.
If the ECU Security Key indicator in the upper lefthand corner of the Health Check screen
displays “Necessary,” navigate to the Main Menu and select the ECU Security Key button as
shown below.
Figure 6.
Figure 7.
© 2025 Lexus, a division of Toyota Motor Sales, USA
L-SB-0035-22
Rev2
August 15, 2022
Page 8 of 11
ECU Security Key Writing
ECU Security Key Writing Process (continued)
3. Select Next to begin ECU Security Key writing.
Figure 8.
4. GTS+ will read the vehicle information. Select Next to send the information to the server.
Figure 9.
© 2025 Lexus, a division of Toyota Motor Sales, USA
L-SB-0035-22
Rev2
August 15, 2022
ECU Security Key Writing
ECU Security Key Writing Process (continued)
5. Select OK to login.
Figure 10.
6. Enter your TIS password and select LOG IN.
Figure 11.
© 2025 Lexus, a division of Toyota Motor Sales, USA
Page 9 of 11
L-SB-0035-22
Rev2
August 15, 2022
ECU Security Key Writing
ECU Security Key Writing Process (continued)
7. Cycle the ignition to IG-OFF, and then IG-ON. Select Next.
Figure 12.
8. Select OK.
Figure 13.
© 2025 Lexus, a division of Toyota Motor Sales, USA
Page 10 of 11
L-SB-0035-22
Rev2
August 15, 2022
Page 11 of 11
ECU Security Key Writing
ECU Security Key Writing Process (continued)
9. Confirm the ECU Security Key has been properly written by performing a Health Check and
confirming the ECU Security Key indicator shows “-”, and then clear ALL DTCs.
Figure 14.
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.
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TSB/Document ID: L-SB-0035-22 Rev2
Replacement Service Bulletin Number:
MFR Communication Date: 2025-01-23
MFR Internal Campaign ID/Software Version: L-SB-0035-22 Rev2
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: ELECTRICAL SYSTEM
MFR Component System:
MFR Component Subsystem:
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