NOx Sensor A0009058509

BG 990727 (OE A0009058509): function on the vehicle

NOx Sensor A0009058509 is supplied by BEST GROWTH under part number 990727, cross-referenced to OE A0009058509, as a direct-fit aftermarket nox sensors. In service it measures nitrogen-oxide concentration and residual oxygen in the exhaust stream and reports both values to the aftertreatment controller over the vehicle data bus. Upstream and downstream readings together set DEF dosing quantity and score SCR conversion efficiency.

BG 990727 is built to the position defined by its OE application on a 12V electrical system in passenger car service on the platform from Mercedes-Benz. Position, calibration and connector layout are part of the specification, so a part that physically fits is not automatically the correct part.

Cable length and connector keying are part of the specification. A cell with correct electrical output but the wrong lead length will not route to the OE bracket.

Fitment for Mercedes-Benz and OE cross reference

BG 990727 replaces 2 OE references: A0009058509 and SNS945, covering cross applications. Always confirm the number printed on the removed part, including any supersession issued by the vehicle manufacturer.

Recorded vehicle coverage for 990727 includes Mercedes-Benz, typically on GLE 350d / GLS 350d 2019-. 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 A0009058509 and quoting the number on your part lets our technical team confirm the variant before despatch.

Symptoms that lead to replacing A0009058509

These complaints bring a vehicle in with the Mercedes-Benz nox sensors under suspicion. None of them prove BG 990727 has failed on its own, which is why the checks below matter before a replacement is ordered.

• no communication with the sensor control module after a cold start
• sensor value frozen at a fixed number once the exhaust warms up
• 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

Checks before fitting BG 990727

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

• 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.
• Compare upstream and downstream NOx readings warmed and under load — idle values prove nothing.

Quality, packaging and ordering 990727

BG 990727 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 A0009058509 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 990727 replace OE A0009058509?

Yes. BG 990727 is listed against A0009058509 and SNS945. Confirm the number printed on the removed part and any manufacturer supersession before ordering.

Which vehicles does BG 990727 fit?

Recorded coverage includes Mercedes-Benz. 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 990727.