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5WK96653B NOx Sensor: A0091530028 Fitment Guide
Is your Actros showing an AdBlue warning with a countdown under it? The cause is usually not the catalyst. It is the NOx sensor — the probe that measures what is left in your exhaust after cleaning.
When that probe drifts, the engine computer reacts as if the cleaning system itself failed. You get warnings, then a distance countdown, then a truck that will not restart. The 5WK96653B NOx sensor for Mercedes-Benz trucks (OE A0091530028) ends that countdown.
What a NOx sensor actually does
A NOx sensor measures nitrogen oxides — the smog gases a diesel engine makes. Your SCR system cleans them out with AdBlue fluid, and the sensor checks the result. One plain job: report the number that proves the cleaning worked.
The cleaning happens in a fixed order:
- Exhaust leaves the engine hot and dirty.
- The DOC — a first-stage catalyst — burns off soot and fuel residue.
- The dosing unit sprays in DEF, sold as AdBlue: a 32.5% urea fluid.
- The SCR catalyst turns the treated NOx into nitrogen and water.
- The NOx sensor sits after the SCR catalyst and reads what came out.
Many trucks run a second sensor before the catalyst as well. The ECU compares both readings to compute cleaning efficiency. That comparison is why one drifting sensor can look exactly like a dead catalyst.
One sensor, three names: order by the number
Truck parts are ordered by number, not by model year. The same sensor circulates under three identities:
| Reference | What it is | Notes |
|---|---|---|
| 5WK96653B | Bosch NOx sensor part number | 24 V heavy-truck unit; stamped on the sensor body |
| A0091530028 | Mercedes-Benz OE number | What the parts catalog prints for your chassis |
| 5WK96653C | Bosch successor variant | Supplier catalogs list it as superseding the B variant |
| Actros MP4 / MP5 | Typical application | 2011 onward, Euro 5/Euro 6 emissions |
Order the number your parts catalog prints for your chassis. If it resolves to a C-suffix sensor, that supersession is correct, not an error. The 24 V 5WK96653B / A0091530028 sensor serves the trucks whose catalogs call up the B variant.
The three fault codes, in plain words
These codes account for most NOx-sensor shop visits:
- P20EE — SCR cleaning efficiency below threshold. The readings say the catalyst is not cleaning. A drifting sensor trips it, but so does a clogged AdBlue injector or an aged catalyst.
- P229B — sensor signal implausible or stuck. The reading contradicts the rest of the system, or freezes at one number. This is the closest thing to a direct verdict on the sensor.
- P20A2 — DEF (AdBlue) system performance. The fluid delivery side is suspect. It shares symptoms with sensor drift because both corrupt the same efficiency math.
Soot is the gray zone. A sensor sooted up by dirty running often reads correctly again after cleaning, then drifts again within weeks. A sensor with a failed internal element never recovers, and replacement is the only repair.
Watch the side effects too: reduced power, higher AdBlue consumption, and a small fuel-economy penalty while the engine runs derated.
Replacing the sensor on the truck
The swap is 30 to 60 minutes of wrench time, plus road time after. Work in this order:
- Order by cross-reference first. Match the OE number your catalog prints for your chassis before the part reaches the bench.
- Disconnect the batteries. A 24 V commercial system can damage electronics during connector work.
- Inspect the harness and connector. Green corrosion or a spread terminal reads exactly like a failed sensor.
- Swap the sensor. Use an oxygen-sensor-style socket, add anti-seize if it is not pre-coated, and do not over-torque the housing.
- Relearn on the road. Clear the codes and run a full drive cycle. The countdown resets once the efficiency number holds in its window.
The wrench time is the easy half. The ECU needs hours of real driving to re-baseline its readings against AdBlue dosing. Plan that road time before you promise the truck back.
The same sensor family across every fleet
Every diesel platform runs this same architecture, and the failure patterns transfer:
- Volvo D11/D13/D16 and Mack MP8 engines → NOx sensor 22303391 / 22014032
- MAN TGX Euro 6 trucks and marine engines → 5WK9 6721B sensor
- Mercedes W166, GLE and ML passenger platforms → A0009053603 NOx sensor (5WK96683D)
- VW Golf VIII and Audi TDI diesels, 2019-2023 → 05N907807A NOx sensor
- Chevrolet Silverado 2500/3500 6.6L Duramax → 12680215 NOx sensor
The diagnostic logic is identical on all of them: test the sensor before you condemn the catalyst. That reasoning runs through our guide to catalytic converters and emission control. Sensors, catalysts and exhaust hardware for every platform sit in the exhaust and emission systems collection.
Two Actros trucks of the same year can need different sensor variants — emissions certification decides the number, not the model year. Write down the OE number from your catalog lookup, or read it off the old sensor body, and match it exactly. Ten minutes of checking beats a second job with the truck back on a lift.
Frequently asked questions
What vehicles does the 5WK96653B / A0091530028 NOx sensor fit?
Mercedes-Benz Actros heavy trucks, MP4 and MP5 generations (2011 onward), on the 24 V electrical system. The reliable check is the cross-reference: if your parts catalog resolves your chassis to A0091530028, this sensor is the match.
What is the difference between 5WK96653B and 5WK96653C?
They are consecutive Bosch variants of the same sensor, and supplier catalogs list the C as superseding the B. Order whichever variant your parts catalog calls up for your chassis number.
Can I keep driving with a failed NOx sensor?
Only until the countdown expires — after that the engine will not restart. Replace it before the countdown runs out, because a roadside no-start with a loaded trailer is the expensive version of the same repair.
What does code P20EE actually mean?
SCR NOx catalyst efficiency below threshold: the sensor readings say the catalyst is not cleaning enough. A drifting sensor is one cause, so validate the sensor before condemning the catalyst.
Can a NOx sensor be cleaned instead of replaced?
Sometimes, briefly. A sooted sensor often reads plausibly again after cleaning, then drifts again; a sensor with a failed internal element never recovers.
Where is the NOx sensor located on an Actros?
Threaded into the exhaust pipe downstream of the SCR catalyst, with the wired sensing module bolted nearby away from direct heat. Trace the harness from the module to find the fitting.
How long does NOx sensor replacement take?
The physical swap runs 30 to 60 minutes, including battery disconnect and connector inspection. The road relearn after it takes a full drive cycle before the countdown clears.
Order the right sensor, end the countdown
The 5WK96653B (A0091530028) for Actros trucks is in stock, along with NOx sensors for Volvo, Mack, MAN, VW and GM diesel platforms. Shipping to a specific chassis? Send us a request for a quote, email support@koeep.com, or WhatsApp +86 181 3883 8291.
- Bosch 5WK9 6653B part numbering and Mercedes-Benz OE reference A0091530028; Actros MP4/MP5 (2011+) Euro 5/Euro 6 fitment — supplier fitment catalogs (eBay, Amazon, Automans, GZTruck)
- 5WK96653C listed as superseding the B variant — LPM UK catalog note
- DTC definitions per SAE J2012: P20EE (SCR NOx catalyst efficiency below threshold), P229B (NOx sensor signal implausible), P20A2 (reductant system performance)
- DEF/AdBlue composition, 32.5% urea — ISO 22241
- NOx sensor failure symptoms and sooting behavior — published diagnostic guides (p20ee.com)
- Sensor drift and cleaning case reports — Peugeot Forums, Reddit r/peugeot diesel threads