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Resources for Tuners

GM/Opel GM2 and GM5 seed key calculator

Calculate diagnostic security access response keys for GM/Opel modules. Choose a supported ECU preset for a 5-byte seed, or enter a known algorithm ID for GM2 or manual GM5 calculations.

Open the seed key calculator Sign in to calculate and copy a response key.

Supported GM/Opel 5-byte ECU presets

Each named preset accepts a 5-byte seed (10 hexadecimal digits) and returns a 5-byte key. E39 and E39A share one preset.

Choose the ECU name that corresponds to your module. The preset selects its calculation automatically; no numeric algorithm ID is needed.

GM2 and manual GM5 algorithm IDs

GM2 uses a 2-byte seed (4 hexadecimal digits) and a 2-byte key. Select GMLAN, Other or Class 2 and enter the known algorithm ID. You can also list supported candidates or compare a captured seed/key pair.

Manual GM5 uses a 5-byte seed and a known algorithm ID. These records accept a final seed byte from 00 to 0A; named ECU presets accept all 5-byte seeds.

Enter an algorithm from 0 to 255 in decimal or with a 0x hexadecimal prefix, for example 135 or 0x87. Unsupported GM2 table slots are identified by the calculator.

Using a calculated key during module programming

Read the seed with your diagnostic equipment, preserve its byte order and calculate the response key. Use your diagnostic interface to send the key and carry out module programming. The website calculates keys; it does not connect to the vehicle.