2021 RAV4 Prime, Sienna Hybrid and Venza Hybrid ECU Security Key Writing T-SB-0111-20


Please see T-SB-0111-20

2021 RAV4 Prime, Sienna Hybrid, Venza Hybrid

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.

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.


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.


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.”

ECU Security Key Writing Process:

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.


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


3. Select Next.


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


5. Select Send.


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.


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


8. Select Ok.


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.