Why NOx Sensors Cause So Many Problems
If you drive a modern diesel, you’ve probably seen a dashboard warning linked to the NOx sensor. These sensors measure nitrogen oxide output in the exhaust and feed data to the SCR system. When they fail, the ECU thinks your vehicle is polluting more than it is. The result? Warning lights, limp mode, and sometimes a no-start countdown.
With replacement costs rising, many drivers ask if a NOx sensor delete is a better option. Let’s look at both choices and weigh up what works best.
Signs of a Failing NOx Sensor
Common symptoms include:
- AdBlue warning lights on the dash.
- Limp mode triggered without clear cause.
- Fault codes like P20EE, P229F, or U029D on diagnostic tools.
- Poor fuel economy after the fault appears.
If you’re seeing these, chances are your NOx sensor is on its way out.
Option 1: NOx Sensor Replacement
Replacement is the standard repair method. The costs vary:
- Generic vans: £350–£500 per sensor.
- Mercedes Sprinter: often £500–£650 each, and some models have two sensors.
- Peugeot Boxer and Citroën Relay: £400–£500 on average.
The upside is your van stays factory standard. Emissions systems remain intact. The downside? Many new sensors fail again within a year, leaving you with the same bill.
Option 2: NOx Sensor Delete
A NOx delete switches the system off inside the ECU software. No sensors are replaced. This option appeals to drivers who are tired of repeat costs and constant downtime.
Benefits of delete include:
- No more NOx sensor fault codes.
- Lower risk of limp mode stopping your workday.
- One-time cost, usually £300–£500, versus ongoing replacements.
- Done via software only — no wires cut or sensors removed.
It’s a permanent fix, but it comes with legal considerations.
Is a NOx Delete Legal in the UK?
Just like an AdBlue delete service, turning off the NOx system counts as an emissions modification. That means:
- DVSA checks: Roadside inspections can issue fines if a system is found disabled.
- MOT tests: At present, MOT stations don’t check NOx sensors directly. If emissions and dash lights are clear, vehicles usually pass.
- Insurance: In some cases, modified emissions systems can complicate claims.
Many drivers still choose deletes because the risk of losing work from breakdowns feels worse than the legal risk.
Delete vs Replacement: Which Is Best?
It depends on your situation:
- Replacement suits you if: You want to keep the van factory standard and plan to sell soon.
- Delete suits you if: You’re keeping the van long-term and want the cheapest fix with no repeat faults.
Both options have pros and cons. The best choice is the one that matches your needs and risk level.
What About Combined Faults?
It’s rare for a NOx sensor to fail alone. Often the AdBlue pump or heater is next. That’s why many drivers go for a full package — a delete of NOx and AdBlue together. It clears all related warnings at once.
For more information, check our SCR system repair page where we cover complete system fixes.
Book a Mobile NOx Sensor Solution
We provide both NOx deletes and diagnostic checks across Leicester and nearby counties. Jobs are carried out at your home or workplace, usually within one to two hours. No need for recovery trucks or garage delays.
Want the NOx warnings gone? Call 07349 821 999 or email info@ifixadblue.co.uk to book today.
Hours: Monday–Sunday, 09:00–20:00
