If you have a spare key, test its operation. If the spare key works consistently, it strongly suggests a problem with the primary key fob. If both keys exhibit the same issue, it points to a problem with the vehicle's BSI system.

: Inability to unlock or lock the doors using the keyless proximity sensors on the door handles.

(a specific sequence of battery disconnection and waiting) to clear these ghost errors. Antenna/Reader Failure:

When the B173D code becomes active, you will generally notice one or more of the following security and electrical symptoms: 1. The Engine Will Not Start

: The engine may refuse to crank entirely, or it might crank for a split second and immediately die.

Code indicates a mismatch. Essentially, the Engine ECU (or another module) is saying, "I am sending a message, but the BSI is either not recognizing me, or the BSI is configured for a different version of this car."

In Peugeot and Citroën vehicles, the fault code specifically indicates a failure in identifying the mechanical or electronic key, or the hands-free remote control located in the reader. This body control fault is managed by the Built-in Systems Interface (BSI) , which is the central computer responsible for security and electronics. Understanding the B173D Fault

is a manufacturer-specific code for key identification failure . It usually points to a dead key battery or a module communication error rather than a major mechanical engine failure. If you need more help, could you tell me:

Hold the key directly against this designated spot and press the Start/Stop button. If the car starts, your vehicle's low-frequency proximity antennas are at fault, or the key fob's internal active transmitter is dead. Step 3: Execute a Peugeot BSI Reset Procedure

: Heavy electrical interference from close aftermarket dashcams, magnetic phone mounts, or local radio towers can break the connection to the key reader. Step-by-Step Troubleshooting and Diagnostic Procedure

Here is the most likely explanation, followed by a summary review of the actual vehicle you probably mean.

Dictates that this code follows PSA Group (Peugeot/Citroën) operational protocols rather than generic OBD-II definitions.

Potentially, . Since this code is directly linked to the immobilizer and can cause the engine to cut off or prevent it from restarting, it is a significant safety risk and a clear sign of a reliability issue. It should be diagnosed and repaired as soon as possible.

The engine may fail to crank or start because the immobilizer is active.

: Sudden battery voltage drops can desynchronize the rolling security code shared between your remote control and the vehicle's immobilizer memory.

: The multi-function screen or driver information cluster displays an explicit warning stating the key is missing or invalid.

: In turn-key Peugeot variants, the copper coil wrapping the ignition barrel (transponder coil reader) can crack or fail over time.