B173d Peugeot -

If this code is present, you may experience:

Use a diagnostic tool (such as Diagbox,

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.

Don’t throw parts at the problem. Follow this professional diagnostic flow:

Tools you need: Multimeter, trim removal tool (or small screwdriver), contact cleaner, and ideally a DiagBox or Lexia 3 scanner (basic OBD readers may not read manufacturer-specific B-codes).

Step 1 – Visual Inspection Locate the air quality sensor. On most Peugeots (308 T9, 208), it is clipped into the front crash bar or behind the lower grille, near the hood latch. Look for physical damage, disconnected wiring, or heavy grime. b173d peugeot

Step 2 – Connector Check Unplug the sensor. Inspect the 3 pins. Are they green or white (corrosion)? Spray with electrical contact cleaner. Reconnect and clear the code. Does it return? If not, corrosion was the issue.

Step 3 – Voltage Test (Key ON, Engine OFF) Using your multimeter, probe the wiring harness connector (sensor disconnected):

If power or ground is missing, check fuses and wiring continuity.

Step 4 – Signal Testing (Simulation) Connect the sensor. Back-probe the signal wire. In clean air, the voltage should be around 1.5V to 2.5V. Spray a small amount of cigarette smoke or a solvent-based brake cleaner near the sensor – the voltage should jump to near 5V. If it doesn’t change, the sensor is dead.

code is indeed an "interesting piece" of Peugeot (and Citroën) diagnostics, as it points directly to a breakdown in the conversation between the car and its key. Technically, it is defined as a Fault in identifying the mechanical/electronic key or the hands-free remote control present in the reader. Why it's a "Head-Scratcher" If this code is present, you may experience:

This code is often seen when a Peugeot refuses to start, but its cause can range from a simple dead battery to complex electronic desyncing: Key Recognition:

The car’s Built-in Systems Interface (BSI) cannot verify the "identity" of the key, often resulting in a "Key Not Detected" message or a complete refusal to crank. Chain Reaction: It frequently appears alongside

(Engine management ECU immobiliser reading error), which means the immobiliser is staying locked because it hasn't received the "all clear" from the key reader. Common Culprits Key Fob Battery:

The most common and easiest fix; a weak battery can prevent the hands-free signal from being strong enough for the reader. The "BSI Glitch":

French car electronics sometimes get "confused." Mechanics often perform a Use a diagnostic tool (such as Diagbox ,

(a specific sequence of battery disconnection and waiting) to clear these ghost errors. Antenna/Reader Failure:

The physical coil or antenna around the ignition barrel (or the hands-free slot) may have failed, meaning it can't "hear" even a perfectly good key. Are you currently dealing with a non-starting vehicle, or are you just digging into the technical side of Peugeot's diagnostic systems?

It seems you are asking for a review of the Peugeot "B173D" — however, no production Peugeot car model is named B173D.

Here is the most likely explanation, followed by a summary review of the actual vehicle you probably mean.

An ounce of prevention is worth a pound of cure.