B173d Peugeot < INSTANT » >
If your vehicle’s dashboard displays messages like "Key Not Detected" or "Immobilizer Fault," and an OBD2 diagnostic scan confirms code B173D, a systematic troubleshooting approach can help identify and resolve the underlying issue. Core Symptoms of Fault Code B173D
: The car may prematurely enter economy mode if the BSI cannot verify the key. Dash Warnings
However, if the code is accompanied by the immobilizer code, your vehicle may refuse to start entirely. This leaves you stranded — definitely not an ideal situation.
A standard battery disconnection can corrupt French vehicle modules if done improperly. Use the official Peugeot BSI reboot procedure to discharge corrupt memory caches:
The exact designation for B173D in official PSA diagnostic framework tools like or Lexia reads: b173d peugeot
or "Electronic Security Fault" messages on the dashboard. The engine cranks but fails to start. Central locking stops working or becomes intermittent. The car may start intermittently.
: Often accompanied by messages like "Electrical circuit fault" or "Battery charge fault". French Car Forum Potential Causes Peugeot BSI Unexpected Reinitialization Fault - Gumtree 8 Dec 2025 —
In Peugeot and Citroën (PSA) vehicles, diagnostic trouble code (DTC) points directly to an immobilizer or key recognition failure . Formally logged by the Built-in Systems Interface (BSI)—the central body control module—the error is defined as a fault in identifying the mechanical/electronic key or the hands-free remote control present in the reader .
Peugeot electronics are notorious for throwing "ghost codes" when the main 12V battery is dying. Low voltage during the start-up sequence can cause the BSI to fail the key identification check. If your vehicle’s dashboard displays messages like "Key
The issue can range from simple battery problems to hardware failures: Weak Key Fob Battery
A: Yes, for short distances. However, you are on borrowed time. Within 500 miles, your DPF will clog, leading to a "risk of particle filter clogging" message and limp mode.
Your Peugeot is a finely tuned machine with complex electronics working behind the scenes. When the BSI can’t identify your key, it’s usually because something small — a fuse, a battery, a ground connection — has failed. Find that small thing, and you’ll find your solution.
Given that the B173D fault relates to data communication, inspect the CAN bus wiring for physical damage. Look for chafed wires, melted insulation near the exhaust, or rodent damage to harnesses. Pay special attention to harnesses running from the BSI to the engine ECU. This leaves you stranded — definitely not an
The car's main computer (BSI) may have a software "hang-up".
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If the code persists across multiple keys and a clean battery reset, professional diagnostics using Peugeot-specific software like will be required to re-program the keys or check the live data streams of the ignition reader coil.
