NOx Sensor 21473997

BG 990599 (OE 21473997): function on the vehicle

NOx Sensor 21473997 is supplied by BEST GROWTH under part number 990599, cross-referenced to OE 21473997, as a direct-fit aftermarket nox sensors. In service it supplies the emissions-monitoring value the OBD system uses to decide whether the SCR stage is still working within its legal window. A drifting cell triggers inducement long before the catalyst itself is worn out.

BG 990599 is built to the position defined by its OE application on a 24V electrical system in truck service on the platform from Volvo. Position, calibration and connector layout are part of the specification, so a part that physically fits is not automatically the correct part.

Fitting position matters as much as the part number: upstream and downstream references often share a housing but carry different calibration data and cable lengths.

Fitment for Volvo and OE cross reference

BG 990599 replaces 2 OE references: 21473997 and 5WK9 6664B, covering cross applications. Always confirm the number printed on the removed part, including any supersession issued by the vehicle manufacturer.

Recorded vehicle coverage for 990599 includes Volvo, typically on FH / FM / FL / FE Truck. Coverage lists are a starting point for identification, not a substitute for checking the OE number on the vehicle.

Where several OE numbers appear against one BG reference, they are supersessions or regional variants of the same specification. Ordering by 21473997 and quoting the number on your part lets our technical team confirm the variant before despatch.

Symptoms that lead to replacing 21473997

These complaints bring a vehicle in with the Volvo nox sensors under suspicion. None of them prove BG 990599 has failed on its own, which is why the checks below matter before a replacement is ordered.

• SCR efficiency below threshold or NOx-signal-implausible fault codes
• DEF over-consumption with no visible leak
• torque derate or speed inducement with a full, in-spec DEF tank
• no communication with the sensor control module after a cold start
• sensor value frozen at a fixed number once the exhaust warms up

Checks before fitting BG 990599

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

• 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.
• After fitting, run the manufacturer's adaptation or relearn so stored efficiency counters reset.

Quality, packaging and ordering 990599

BG 990599 is manufactured and tested to aftermarket replacement standards, with electrical, leakage and functional testing carried out before packing on the 24V specification. Bulk and retail packaging, private-label cartons and customer-specific labelling are available for distributors and workshop groups.

Send OE 21473997 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 990599 replace OE 21473997?

Yes. BG 990599 is listed against 21473997 and 5WK9 6664B. Confirm the number printed on the removed part and any manufacturer supersession before ordering.

Which vehicles does BG 990599 fit?

Recorded coverage includes Volvo. It is supplied as a direct-fit aftermarket nox sensors on 24V 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 990599.