NOX SENSOR 9821121180 9675358480 3552345 3642241 SU001-A7559 SU001-A3624

Get your Citroën back to correct AdBlue dosing and emission control on modern diesels with this replacement nox sensor, also referenced in service manuals as the nitrogen oxide sensor or exhaust NOx probe. Built to OEM specification, matching 9821121180, 9675358480, 9821120980, 3552345 and 3642241. Also fits equivalent DS, Peugeot and Opel models.

Common signs of failure

A failing NOx sensor on diesel vehicles typically triggers fault codes P220A, P220B, P220C, P229F or P207F (NOx sensor circuit / SCR system efficiency). Drivers see the engine warning light come on, an AdBlue or 'Emissions' warning on the dashboard, often a countdown 'Vehicle will not start in X miles' message, and in many cases the vehicle entering limp mode. Left unaddressed, the ECU will eventually prevent the engine from restarting until the fault is cleared.

Fitment notes

Direct-fit replacement, with the original wiring harness and ECU connector. After fitting, the sensor needs a short re-learn drive cycle (typically 5–20 minutes of motorway driving) for the ECU to calibrate to the new probe. Some manufacturers recommend resetting adaptations with a diagnostic tool — useful but not strictly required on most models. Standard 5 pin connector. Position: Before catalytic converter, After catalytic converter.

Frequently asked questions

Where is the NOx sensor located?

Most diesel vehicles have two NOx sensors: one upstream and one downstream of the SCR catalyst/AdBlue injection point. Identify whether your fault is for the inlet or outlet sensor (the code and live data will tell you) before ordering.

Will it fix my limp-mode and AdBlue warning?

Yes, if the fault code points to the NOx sensor itself. After fitting, clear the codes and complete a regen drive cycle — warnings usually clear within a few miles.

How long do NOx sensors last?

Typically 80,000–120,000 miles, though heavy stop-start driving and poor-quality AdBlue can shorten lifespan. Replacement at the first sign of failure prevents the vehicle locking you out.