Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Immobilizer System: Introduction
If ignition key, immobilizer-ECU or PCM is replaced, or an ignition key is added, encrypted codes of all the ignition keys must be registered. A maximum of 8 ignition keys may be registered. See FUNCTION SELECTION .
If PCM is replaced, immobilizer-ECU should also be replaced. Each PCM has an encrypted code for immobilizer-ECU. The PCM encrypted code is registered in immobilizer-ECU using MUT-II Scan Tool (MB991502). If immobilizer-ECU has been replaced, scan tool must be used to input password. See FUNCTION SELECTION . Obtain current password from vehicle owner.
Key ID registration (encrypted code) and password set are entered from special function menu. If key ID registration (encrypted code) and password set cannot be used, check for DTCs. After repairs, continue with special function menu selection(s).
If wrong password is entered 5 times in a row, immobilizer-ECU will determine an unauthorized operation is being attempted. Start-prevention mode will be set, engine operation will stop, and all special functions will be disabled. If ignition switch is turned to ON position and left on for about 20 minutes, start-prevention mode will be cancelled.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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