BMW Immobilizer

Supported coding features by BimCOM diagnostic tool https://www.obdtester.com/bimcom

Abbreviations

DME=Digital Motor Electronics

DDE=Digital Diesel Electronics

EWS=Electronic drive-away protection

CAS=Car access system (immobilizer)

Generations

• DME/DDE and EWS ECU
• EWS2
• EWS3
• EWS3D
• DME/DDE and CAS ECU

DME/DDE and EWS synchronization

Two values, one fixed, one rolling. Coding must be performed in both engine (DME/DDE) and immobilizer ECU at the same time, otherwise immobilizer not allowing start.

Incorrect synchronization usually results in DTC "2737 EWS manipulation protection"

Rolling Code Synchronisation

What it does

• Resynchronises the rolling code between:
• Key transponder
• Immobilizer module (EWS/CAS)
• Engine control unit (DME/DDE)
• Restores communication when codes fall out of sync
• Allows proper engine start authorization

Why it is required

• Rolling codes can desynchronise after:
• Low battery events
• Battery replacement
• Long-term storage
• Faulty starts or weak key signal
• When out of sync:
• Engine cranks but does not start
• Immobilizer warning may appear

Conditions that must be met

• Key battery must be functional and detectable
• No active EWS/CAS communication faults
• EWS/CAS and DME/DDE must be matched as a valid pair
• Stable vehicle voltage (charger recommended)
• Antenna ring functional

When the synchronisation is used

• After key replacement
• After CAS/EWS or DME/DDE replacement (when matched already)
• After repairing immobilizer wiring issues
• When “crank–no start” occurs due to immobilizer lockout

What happens during the procedure

• Diagnostic tool requests new rolling code alignment
• Immobilizer and engine ECU exchange:
• Current rolling codes
• Secret key data
• Synchronization counters
• Both modules store updated matching codes

If the procedure is not performed

• Engine may not start
• Key authorization may fail intermittently
• Immobilizer faults may appear under DME/DDE or CAS/EWS
• Vehicle may enter anti-theft lock state

After the synchronisation

• Test engine start with all keys
• Check for immobilizer fault codes
• Verify stable key recognition
• If issues persist:
• Key transponder may be defective
• Antenna ring may have weak signal
• CAS/EWS–DME alignment may be required

Coverage in BimCOM