In this story, the fix turns out to be a classic Peugeot quirk: a corroded connection on the Battery Power Supply Protection Unit
Damaged wiring between the keyless antenna and the BSI.
Replacing the switch is the most common "work" associated with B173D. Locate the switch under the driver-side dashboard. b173d peugeot work
Even if it cranks, low voltage can cause ECU communication failures. 4. Symptoms
If you are stuck with a Peugeot that won't start due to B173D, use this progressive troubleshooting protocol: Step 1: Use the Emergency Backup Slot In this story, the fix turns out to
When the BSI generates a code, it is specifically telling you that there is a "Fault In Identifying The Mechanical/Electronic Key Or The Hands-free Remote Control Present In The Reader." The "Reader" is the antenna coil around your ignition barrel that detects the chip in your key.
Modern Peugeot models are highly sensitive to voltage drops. If the main 12V engine battery’s state of charge falls below a critical threshold, the BSI will systematically shut down accessory modules—including the hands-free keyless antenna network—to save power, resulting in a false-positive B173D code. 3. External Radio Frequency (RF) Interference Even if it cranks, low voltage can cause
Finally, . The fix might be as simple as repairing a broken wire in the rubber boot between the door and the chassis (a classic Peugeot failure point) or as involved as reprogramming a replacement BSI—a process that requires downloading the vehicle's specific configuration from Peugeot’s servers and pairing it with the immobilizer transponder key.
Diagnostic Trouble Code (DTC) B173D is a body-system fault code closely tied to the immobilizer system. When you press the start button or insert the key, the car initiates a security handshake.
malfunctions (won't lock/unlock automatically). Engine cuts out while driving (less common, but possible). Common Causes of B173D