B173d Peugeot Now

The fault code B173D in Peugeot and Citroën vehicles is a diagnostic trouble code (DTC) typically related to the immobilizer system or key recognition . What the Code B173D Means

3. Broken Glow Plug Harness

The wiring harness that connects the glow plug control unit to the four glow plugs sits directly on top of a hot diesel engine. Over time (60,000+ miles), the insulation becomes brittle. The wire leading to Cylinder 4 often rubs against the engine cover or a fuel line, snapping internally. You may see no external damage, but a continuity test will reveal the break. b173d peugeot

  1. Persistent Check Engine or Service Light: The amber engine/Service light illuminates and stays on. In some models, a message like "Air Quality Fault" appears on the central display.
  2. Manual Recirculation Only: You can manually press the recirculation button, but the car never switches to recirc automatically, even behind a smoky truck.
  3. Musty or External Smells Entering Cabin: Since the system fails to close the fresh air flap, exhaust fumes, dust, and odors enter the cabin freely.
  4. Error Code Storage: The fault is stored in the BSI. If cleared, it often returns immediately or within one driving cycle.
  5. Potential Parasitic Battery Drain (rare): If the sensor has internally shorted, it can keep the BSI network active, slowly draining the battery overnight.

This code is common across PSA Group vehicles (Peugeot and Citroën) and generally prevents the engine from starting because the security system does not "see" a valid key. The car will not start or crank. The fault code B173D in Peugeot and Citroën

Safety Implications

  • If B173D is active → Passenger airbag will be disabled (default safe state in case of OCS fault).
  • ➡️ An adult passenger may not be protected in a crash.
  • Do not ignore this code or simply turn off the warning with a scanner without repairing.

BSI Communication Glitch: The BSI (the car's central "brain") may have lost its coding or is failing to communicate with the engine ECU. Troubleshooting Steps Before heading to a specialist, try these DIY fixes: Electrical circuit fault: have your vehicle repaired Persistent Check Engine or Service Light: The amber

What is the B173D Peugeot error code?

Starting Issues: The engine may fail to start or the dashboard may display a "key not detected" warning.