NOx Sensor 4M0907807AL

BG 990784 (OE 4M0907807AL): function on the vehicle

NOx Sensor 4M0907807AL is supplied by BEST GROWTH under part number 990784, cross-referenced to OE 4M0907807AL, 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 990784 is built to the position defined by its OE application on a 12V electrical system in passenger car service on the platform from Volkswagen. 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 Volkswagen and OE cross reference

BG 990784 replaces 2 OE references: 4M0907807AL and SNS777, covering cross applications. Always confirm the number printed on the removed part, including any supersession issued by the vehicle manufacturer.

Recorded vehicle coverage for 990784 includes Volkswagen, typically on Q7 / Q8. 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 4M0907807AL and quoting the number on your part lets our technical team confirm the variant before despatch.

Symptoms that lead to replacing 4M0907807AL

These complaints bring a vehicle in with the Volkswagen nox sensors under suspicion. None of them prove BG 990784 has failed on its own, which is why the checks below matter before a replacement is ordered.

• 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
• SCR efficiency below threshold or NOx-signal-implausible fault codes

Checks before fitting BG 990784

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

• 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.
• Confirm supply voltage, ground quality and bus termination before condemning the sensor module.
• 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.

Quality, packaging and ordering 990784

BG 990784 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 4M0907807AL 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 990784 replace OE 4M0907807AL?

Yes. BG 990784 is listed against 4M0907807AL and SNS777. Confirm the number printed on the removed part and any manufacturer supersession before ordering.

Which vehicles does BG 990784 fit?

Recorded coverage includes Volkswagen. 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 990784.