: Low vehicle battery voltage can cause "ghost" electrical faults in Peugeot's sensitive electronics. Ensure the battery maintains roughly when the engine is off.
An "Immobiliser Fault" or "Key Not Detected" message may appear on the dashboard. The central locking might behave erratically. Common Causes: Weak Key Battery: b173d peugeot
Fault code is a body control / airbag system diagnostic trouble code (DTC) specific to Peugeot (and other PSA group vehicles like Citroën, DS, and sometimes Opel). It indicates a malfunction within the Occupant Classification System (OCS) — specifically, the system is unable to reliably confirm the "seat occupied" status of the front passenger seat . : Low vehicle battery voltage can cause "ghost"
If voltage tests show no power, trace the two wires back to the BSI (under the dashboard). This is tedious. A professional auto electrician will charge ~$80 to repair a broken wire. Do not attempt unless you have wiring diagrams. The central locking might behave erratically
Modern Peugeots are equipped with an automatic climate control system. When you set the HVAC to "Auto," the system monitors outside air quality. If the sensor detects high levels of pollutants (diesel fumes, CO, NOx), it automatically switches the ventilation from fresh air to to protect the cabin occupants.
The sensor itself is an electromechanical component that heats an element to detect pollutants. Over time (typically 5-8 years), the sensing element burns out or becomes contaminated with oil or road grime. This is the number one cause of the b173d Peugeot code.