The EDC15 “login” and EDC16 “security access” in Volkswagen and Audi vehicles are often confused, but they are distinct functions. Unlike EDC15, EDC16 doesn’t have manual adaptation channels; adaptations are automatic, often called “ECU learning.” However, EDC16 incorporates security layers to protect diagnostic routines like reading, writing, and flashing the ECU.
Decoding EDC16 Security Access
Accessing these routines requires a specific command sequence from diagnostic tools like VCDS. The ECU responds to access requests with a password prompt. Incorrect password entries lead to a “negative response” (7F) with a “wrong password” reason code. Four consecutive incorrect attempts trigger a security lockout.
Security Lockout and the VCDS Access Key
Once locked, even the correct Vcds Access Key won’t grant access. The ECU will refuse the session (7F response) with a “requiredTimeDelayNotExpired” (37) reason code. The full response string (7F,27,37) signifies a negative response (7F) to a security access request (27) due to the time delay (37). Tools like Q-loader might display this as error 01 02, pointing to the specific step where the error occurred. The detailed error string, often encrypted, requires specialized interpretation.
The lockout duration starts at 20 minutes, doubling with each subsequent failed attempt, reaching a maximum of 255 minutes (over 4 hours). Some tuning companies might intentionally set this maximum delay as a form of read protection.
Example of a VCDS Security Access Error
Resetting the Lockout and Gaining Access
To reset the lockout:
- Keep the diagnostic interface connected and “handshaked.”
- Leave the ignition key ON (engine OFF).
- Keep the driver’s door open.
- Wait for the required time delay (often 40 minutes, but potentially up to 4 hours 15 minutes).
After the delay, the correct password, 12233 for VCDS, can be entered through the “security access” subroutine. Alternatively, using a dedicated flash tool often automates this process by inputting the correct access code.
Car with Diagnostic Tool Connected for Security Lockout Reset
This time delay acts as a security measure, preventing unauthorized access and potential damage to the ECU. The value for this delay is stored in the EEPROM, separate from the flash memory containing tuning data, allowing for read protection without affecting performance modifications. While not foolproof, it provides a significant barrier against unauthorized access. Understanding the intricacies of EDC16 security access and the role of the VCDS access key is crucial for anyone working with these systems.
