Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
Your car has a special lock that talks to the key to make sure it's the right one. If this lock can't talk to the key properly, the car won't start.
The Electronic Immobilizer System (EWS) is responsible for ensuring that the vehicle's key is authorized to start the engine. If the start value is destroyed, the system cannot verify the key.
The P1668 code indicates a failure in the EWS system where the start value, which is a digital code used to verify the key's authenticity, has been corrupted or destroyed. This prevents the engine from starting as a security measure.
• Engine does not start
• Security light illuminated
• No response from ignition
• Faulty EWS module
• Corrupted EWS data
• Faulty key transponder
EWS: Electronic Immobilizer System
Transponder: A device that communicates with the EWS to verify the key
• Check for other related codes
• Inspect the key and EWS module for damage
• Test the communication between the key and EWS
• Reprogram the EWS module
• Replace the faulty EWS module
• Replace or reprogram the key
• OBD-II scanner
• Digital multimeter
• EWS programming tool
$200 - $500
Moderate
• BMW 3 Series
• BMW 5 Series
• BMW X5
• Regularly check key and EWS system for wear
• Avoid exposing keys to extreme temperatures
• Keep software updated
Security System Issue
• Have a spare key available
• Consult a professional if the car doesn't start
• Avoid tampering with the EWS system
Check vehicle warranty for coverage on electronic components.
This code has been more prevalent in older BMW models with early EWS systems.
High – The vehicle will not start, requiring immediate attention.
Ensure repairs are conducted by qualified personnel to avoid security risks.
• Ignition in the ON position
• Attempt to start the vehicle
The EWS module is typically located near the steering column or under the dashboard.
Q: Can I start my car with this code?
A: No, the car will not start until the issue is resolved.
Q: Is this a common issue?
A: It can occur in older models with aging EWS systems.
Pro · Four-system diagnostics
A handheld scanner aimed at engine, transmission, ABS, and airbag diagnostic work.
Chassis and ABS faults usually need a scanner that can read brake-system data directly.
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Universal · Torque wrench
Useful when reassembly torque matters for wheel, suspension, and under-hood fasteners.
Useful when wheel, hub, or suspension hardware needs correct reassembly torque.
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Universal · Drive-on ramps
Helpful for safer access underneath the vehicle during exhaust, EVAP, and underbody inspection work.
Helpful for safer access during underbody inspection work.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.
Fitment Required · Vehicle-fitment part
Commonly relevant for misfire, ignition-efficiency, and some drivability-related repairs.
Misfire and ignition-related faults commonly involve spark plugs as part of the repair path.
Check the correct plug type, gap, and engine application for your vehicle.
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Fitment Required · Vehicle-fitment part
Relevant when the fault points toward ignition-coil performance or cylinder-specific ignition issues.
Some ignition faults involve coil performance or cylinder-specific coil problems.
Match the coil to your engine and confirm the failed component before ordering.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.