Fault code P1615 – a step-by-step guide to diagnosing and fixing it

Error code P1615 is displayed and the check engine light is on - what does this mean?

The DTC P1615 is recognized by the OBD/EOBD system if there is a problem with the start release or the immobilizer system. This manufacturer-specific trouble code mainly affects the engine control unit and communication with the immobilizer. This fault code can have different meanings for different manufacturers, but usually refers to authentication problems between the key and the vehicle.

What causes can this fault code have?

• Defective or non-programmed vehicle key
• Faulty immobilizer or transponder
• Damaged engine control unit (ECU)
• Broken cable connections in the immobilizer system
• Defective antenna on the ignition lock
• Corroded or loose plug connections
• Faulty communication between control units
• Weak or flat vehicle battery
• Defective ignition lock or start switch

What symptoms occur in parallel with fault code P1615?

• Starting problems: The vehicle will not start or the engine will not start even though all other systems are working. Immobilizer activated: The immobilizer prevents the engine from starting even with the correct key. Check engine light: The check engine light is permanently illuminated or flashing. Warning messages: Messages such as "Key not recognized" or "Start enable denied" appear in the display. Electrical problems: Various electrical systems may function irregularly or fail.

How can the problem with error code P1615 be rectified?

• Repairing EOBD code P1615 usually requires a systematic diagnosis of the immobilizer and starting system.
• Reprogram the keys: Have all vehicle keys relearned and reprogrammed at a specialist workshop to restore communication with the immobilizer.
• Reset the immobilizer: Perform a complete reset of the immobilizer and synchronize it with the engine control unit using appropriate diagnostic equipment.
• Battery test and replacement: Check the vehicle battery for sufficient voltage and replace it if necessary, as weak batteries can cause communication problems.
• Check cable connections: Check all cable connections between the immobilizer, ignition lock and engine control unit for damage, corrosion or loose connectors.
• Replace engine control unit: If the ECU is defective, it must be replaced and then reprogrammed with all vehicle keys and the immobilizer.
• Replace ignition lock antenna: Replace the transponder antenna on the ignition lock if it is defective and no longer recognizes the key.