NOx Sensor 9821120780

BG 201609 (OE 9821120780): function on the vehicle

NOx Sensor 9821120780 is supplied by BEST GROWTH under part number 201609, cross-referenced to OE 9821120780, as a direct-fit aftermarket nox sensors. In service it acts as the closed-loop feedback element of the SCR circuit: it tells the controller how much NOx is still leaving the catalyst, so dosing is trimmed up or down instead of running to a fixed map.

BG 201609 is built to the position defined by its OE application on a 12V electrical system in passenger car service on platforms from Peugeot, Citroën and Renault. Position, calibration and connector layout are part of the specification, so a part that physically fits is not automatically the correct part.

The measuring cell is consumable. Soot loading, silicone contamination and repeated thermal shock all shorten its life, which is why a sensor can drift for months before it sets a hard code.

Fitment for Peugeot, Citroën and Renault and OE cross reference

BG 201609 replaces 1 OE reference: 9821120780. Always confirm the number printed on the removed part, including any supersession issued by the vehicle manufacturer.

Recorded vehicle coverage for 201609 includes Peugeot, Citroën and Renault, typically on 308 II / 508 II / 3008 / 5008 1.5-2.0 BlueHDi. Coverage lists are a starting point for identification, not a substitute for checking the OE number on the vehicle.

Quote the number printed on your part with the engine code when you enquire; a single-reference part is the most common source of ordering errors when a platform received a mid-life update.

Symptoms that lead to replacing 9821120780

These complaints bring a vehicle in with the Peugeot and Citroën nox sensors under suspicion. None of them prove BG 201609 has failed on its own, which is why the checks below matter before a replacement is ordered.

• dosing shut-down after a few minutes of steady-state running
• upstream and downstream values reading almost identically under load
• intermittent fault that clears after the engine cools and returns when hot
• SCR efficiency below threshold or NOx-signal-implausible fault codes
• DEF over-consumption with no visible leak

Checks before fitting BG 201609

Aftertreatment faults are usually system faults. Working through these checks prevents a repeat failure after the new nox sensors is fitted.

• Inspect the harness for heat damage and the connector for moisture and green corrosion.
• Check for exhaust leaks ahead of the sensor boss; a diluted sample reads low NOx.
• Read the sensor's own dew-point release time — a cell that never heats is a supply or module fault.
• Verify DEF concentration with a refractometer before blaming the measuring cell.
• Check for a pending software or parameter update for the sensor control module on that platform.

Quality, packaging and ordering 201609

BG 201609 is manufactured and tested to aftermarket replacement standards, with electrical, leakage and functional testing carried out before packing on the 12V specification. Bulk and retail packaging, private-label cartons and customer-specific labelling are available for distributors and workshop groups.

Send OE 9821120780 or the number printed on your part, the engine code and the vehicle identification number with your enquiry, and our technical team will confirm the correct reference, current stock position and lead time before you commit to an order.

Frequently asked questions

Does BG 201609 replace OE 9821120780?

Yes. BG 201609 is listed against 9821120780. Confirm the number printed on the removed part and any manufacturer supersession before ordering.

Which vehicles does BG 201609 fit?

Recorded coverage includes Peugeot, Citroën and Renault. It is supplied as a direct-fit aftermarket nox sensors on 12V systems. Adaptation, reset or relearn procedures required by the vehicle manufacturer still apply after installation.

Does this fault code always mean the nox sensors has failed?

No. Exhaust leaks, wiring and connector damage, reductant quality, dosing performance and upstream engine faults can all produce the same codes. Validate those inputs before replacing BG 201609.