NOX OFF

The NOX OFF disables upstream/downstream NOx-sensor monitoring — the standard companion to an AdBlue/SCR delete when the sensors are removed or failing.

NOx sensors bookend the SCR catalyst — one upstream, one downstream — and they are among the most fragile electronics in the exhaust. A failed sensor element, heater or control module logs faults in the P2200–P2209 and U02xx ranges and, because the SCR strategy depends on their readings, drags the AdBlue inducement countdown down with it.

The NOX OFF patch removes the sensor monitoring chain: element and heater plausibility, communication faults, and the derate/countdown triggers tied to them — while leaving the rest of the calibration untouched. It is the right fix when only the sensors are defective and the dosing hardware is still sound.

When the whole SCR system is being removed, NOX OFF is applied inside the full AdBlue OFF patch — but as a standalone service it solves the common case of repeated sensor replacements at sensor price every few months.

Sensor position matters: upstream and downstream channels are monitored by different routines, and the patch covers both — element signal, heater circuit and the CAN communication check that reports a dead sensor module. Because the inducement chain listens to the sensors, removing the monitoring removes the countdown cleanly.

On systems where the sensors still do useful work this is a surgical patch; on full SCR removals it is one component of the AdBlue OFF job. Either way the sensor chain's faults, heaters and communication checks are removed consistently.

The sensor modules sit on their own CAN address — which is why a dead module produces communication faults (U029D) alongside the element codes. The patch removes the module's expected presence entirely, so unplugging it later is equally silent.

Bosch DCU15 and DCU17 PC42/PC43, MD1/MDG1 engine ECUs with integrated SCR monitoring, Continental ACM2.1/MCM2.1 on Mercedes-Benz and EDC17 SCR applications — passenger cars, vans, trucks and agricultural platforms.

Typical jobs: VW/Audi TDI with SCR, Mercedes-Benz CDI/BlueTEC, PSA BlueHDi, Ford TDCi, Renault dCi — plus truck and agricultural platforms on DCU17 and ACM2.1/MCM2.1.

Read the engine ECU — and the DCU dosing module where the system uses one — in bench or OBD mode with FLEX or KESS3, upload, patch and write back. The sensors can stay fitted or be unplugged; no fault returns either way.

NOX OFF vs AdBlue OFF: sensors only vs the complete SCR delete. When the rest of the dosing hardware is healthy and just the sensors keep dying, NOX OFF is the surgical fix; retiring the whole SCR system calls for AdBlue OFF.