The EDC16 engine control unit (ECU) utilizes a security access system to protect critical diagnostic functions like reading, writing, and flashing. This system differs significantly from the simpler login procedure found in older EDC15 systems. Understanding how EDC16 security access works, particularly with VCDS, is crucial for anyone working with these ECUs.
EDC16 Security Access: Not Just a Login
Unlike the manual adaptation channels in EDC15, EDC16 ECUs handle adaptations automatically through “ECU learning.” While there are basic settings that allow some adjustments, directly modifying stored values in the EEPROM (diagnostic memory section) isn’t possible like in EDC15. The ECU manages these changes internally.
The security layer in EDC16 controls access to diagnostic routines, including flashing. When a diagnostic tool like VCDS attempts to initiate a session (e.g., reading codes, identifying the ECU, or flashing), the ECU demands a security access code – essentially a password.
Security Lockout and Time Delays
Entering the wrong security access code in VCDS triggers a counter within the ECU. Four incorrect attempts result in a security lockout, denying any further access, even with the correct code. This lockout is indicated by a “7F” response code, alongside a reason code “37” signifying “requiredTimeDelayNotExpired.” The full response string is 7F,27,37, where:
- 7F: Negative response (session refused).
- 27: Security access requested.
- 37: Required time delay not expired. Error code 01 02 in Q-loader corresponds to this error.
The lockout duration starts at 20 minutes and doubles with each subsequent set of failed attempts, reaching a maximum of 255 minutes (over 4 hours). During this period, the ECU remains locked, regardless of the code entered.
Resetting Security Access Lockout
An example of a VCDS interface connected to a vehicle’s OBD-II port.
To reset the lockout:
- Maintain Connection: Keep the diagnostic interface (e.g., VCDS cable) connected and communicating with the vehicle.
- Ignition On: Leave the ignition key in the “on” position (engine off).
- Open Door: Ensure at least one vehicle door is open.
- Wait: Wait for the required time delay to expire. This is usually 40 minutes, but it can be up to 255 minutes in cases of repeated incorrect attempts.
A screenshot of a VCDS software interface displaying diagnostic information.
After the delay, the correct security access code can be entered to regain access. For VCDS, this code is typically 12233, entered via the “Security Access” function. Flashing tools often automate this process by inputting the code automatically.
Some tuning companies might intentionally set the lockout time to the maximum 255 minutes as a form of read protection, preventing unauthorized access to the ECU’s diagnostic routines.
Key Takeaways
Understanding the EDC16 security access system is vital for successful diagnostics and tuning. Remembering the correct VCDS security access code (12233) and the procedure for resetting a lockout will save you time and frustration. Always exercise caution when attempting to access sensitive ECU functions to avoid triggering a security lockout.
