In Peugeot (and broader PSA Group) vehicles, the fault code primarily identifies a communication or authentication failure within the vehicle's immobilizer system
: Because the BSI handles transponder data and remote entry codes simultaneously, door locking mechanisms may function sporadically. Root Causes Behind the Fault Code
: The car might work flawlessly for weeks, and then randomly fail to recognize the key, forcing you to lock, unlock, and wait before it resets.
In Peugeot-Citroën (PSA) diagnostics, is defined as an "Error identifying the mechanical / electronic key or hands-free remote control located in the reader" .
After addressing any voltage or fuse issues, clear all fault codes using a compatible diagnostic tool (Diagbox is preferred, but many generic OBD2 scanners can read and clear manufacturer‑specific codes). Then drive the vehicle for 15–20 km. Re‑scan to see if B173D returns. If it does, note whether it appears alone or with other codes. b173d peugeot work
BSI (Body Control Unit), Immobilizer, Keyless Entry Antenna/Receiver. 3. Common Causes
Some owners have discovered that the act of plugging in an OBD diagnostic tool at a test centre can trigger B173D and other codes. This suggests a momentary interruption of CAN bus communications.
: The ring antenna located around the ignition barrel (or near the Start button) may be faulty or disconnected. BSI Configuration or "Telecoding" Issues
Diagnostic and Repair Analysis of the B173D Fault Code in Peugeot Vehicles In Peugeot (and broader PSA Group) vehicles, the
+------------------+ Wireless Handshake +------------------------+ | Key Transponder | <========================> | Ignition Reader/Slot | +------------------+ +------------------------+ | | Fob Battery? Wiring Loom? v v +------------------------+ +------------------------+ | BSI (Central Module) | <==================> | ECU (Engine Management) | +------------------------+ Immobilizer Signal +------------------------+ 1. Key Fob and Transponder Issues
The BSI is a central gateway for many vehicle systems. When it experiences a voltage or communication glitch, it may log codes for all the systems it manages. Fixing the root cause (e.g., weak battery) will clear all those codes.
: A weak or dead battery in the remote is the most common and easiest cause to fix.
[Key Fob / Transponder] ──(Wireless Signal)──> [Ignition Switch Reader / Slot] │ (Data Packet) ▼ [Engine Management ECU] <──(Validation Request)─── [BSI Computer] After addressing any voltage or fuse issues, clear
Dropping the key fob can damage the transponder chip or the circuit board inside.
by a dealer if you experience recurring electrical gremlins.
This comprehensive guide breaks down exactly what the fault code means, how the immobilizer system works, common symptoms, diagnostic steps, and practical solutions to get your vehicle back on the road. What Does Fault Code B173D Mean?