The key itself may be at fault: a worn‑out transponder chip, a damaged internal circuit board, or simply a low battery in the remote key fob. After changing the key fob battery, the key may need to be re‑synchronised with the BSI.
Dropping your key fob can dislodge or crack the delicate, surface-mounted transponder chip inside the key housing, corrupting the physical transmission of the security code. How to Get Your Peugeot Working: Step-by-Step Diagnostics
: This "soft reset" can clear communication errors without tools. Open the driver's window and turn off all electronics.
B173D Manufacturer: Peugeot / Citroën (PSA Group) System: Body Control Module (BCU/BSI) / Locking Architecture Description: Lock Assembly / Door Lock Signal Plausibility Error Variant: Often accompanied by suffixes like 5A (Upper Limit) or 4A (Signal Invalid). b173d peugeot work
A dying battery in the key fob (CR2032) causes a weak signal, preventing the car from recognizing it properly 1.2.1 .
Once the repair is complete:
If the code persists after a battery reset and a fresh key battery, the issue may lie deeper in the BSI software or the ignition barrel antenna. The key itself may be at fault: a
In simple terms, your Peugeot’s main computer—the BSI (Built-in Systems Interface)—is experiencing a with your car key or the vehicle's immobilizer system. This is not just a dead battery in your key fob; it indicates the vehicle's security network has a glitch or intermittent failure that can cause a wide range of bizarre electrical symptoms.
Understanding and Fixing the B173D Peugeot Fault Code: A Comprehensive Guide
Issues in the wiring harness connecting the BSI to the key reader or antenna. B173D Peugeot Troubleshooting & Repair Steps How to Get Your Peugeot Working: Step-by-Step Diagnostics
The key fob broadcasts an encrypted security token.
: Your main key has a dead transponder chip or a compromised circuit board.
If all the above fail, a more advanced diagnostic session is required:
Stop the car, remove the key (if necessary), and close all doors. Wait for 3 minutes for the BSI to enter sleep mode. Disconnect the negative battery terminal. Wait at least 5 minutes. Reconnect the battery and wait another 2 minutes. Try starting the car. 5. Check for Antenna Obstructions
Before dismantling your vehicle's dashboard, isolate whether the problem lies with the car or the remote key fob. Locate your vehicle's physical backup or spare key and try starting the car.