If you send the wrong Key too many times, the ECU will "lock" itself for a set period (usually 10 to 30 minutes). You must leave the ignition on and wait for the timer to expire before trying again.
If you are trying to bypass a GM 5-byte security wall and keep getting "Security Access Denied," check the following: gm 5 byte seed key
The algorithm uses XOR, Bit-Shifting (Left/Right), and Additions to scramble the Seed. If you send the wrong Key too many
Different modules (Engine, Transmission, Body Control) may use different algorithms or "Security Levels" even within the same vehicle. Tools for Calculating the Key Different modules (Engine
The tool runs that 5-byte Seed through a proprietary mathematical algorithm.
The ECU generates a random 5-byte hexadecimal number (the "Seed") and sends it back to the tool.
