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NOx Sensor Replacement
Typical Cost: Medium
Mobile Repair? Yes
Typical Lead Time: 1-2 days depending on part availability
What does a NOx sensor do?
NOx is the chemical term given to the nitrogen oxides that cause air pollution, nitric oxide (NO) and nitrogen dioxide (NO2)
During the combustion cycle of diesel engines, harmful NOx is created and expelled out the exhaust. The NOx sensor forms part of the Selective Catalytic Reduction (SCR) system and is positioned before the catalytic converter and monitors the amount of the harmful gasses being produced. This information is then fed back to the SCR system in order to fine tune the addition of the fluids (e.g. AdBlue) that is injected into the system to reduce the emissions.
A similar use of a NOx sensor is used on petrol engines as well to alter the fuel/air ratio to reduce emissions in combination from the readings of the O2 (or Lambda) sensor.
What happens if a Nox sensor fails?
In most cases the engine light will come on and the vehicle’s performance will be limited to “limp home mode” until the fault is rectified. In some cases, it may mean the engine will not re-start either.
How do I know if a Nox sensor needs replacing?
Without having the fault diagnosed, it is unlikely that you can know for certain that the NOx sensor is the cause of the fault.
So what needs to be done?
Firstly a professional diagnostic must be carried out. As these sensors are not cheap, we would not recommend going ahead with a replacement based on the results of a home error code reader. However, once the cause of the fault has been confirmed, the replacement of the NOx sensor is the only option, these units cannot be repaired.
What happens during a Nox sensor replacement?
The process may differ slightly between vehicles but generally the mechanic will do the following;
* The mechanic will check to confirm that the NOx sensor requires replacement
* Careful extraction of the NOx sensor will be carried out
* A new NOx sensor will be installed
* Error codes will then be cleared and system tested
What does the quote for a Nox sensor replacement cover?
Unless otherwise stated, the quote for a NOx sensor replacement will cover;
- The cost of the NOx sensor
- Coming to you
- Fitting of the parts
- Disposal of the old parts (unless you request to keep them)
- VAT (if applicable)
- 12 months parts and labour warranty
What to search for on the ClickMechanic site?
Diagnostic inspection
NOx sensor replacement
How much does a Nox sensor replacement cost?
As each NOx is dependent on what options are installed, we need to price this manually so once you have selected the option from the website, please fill out the price request form and we will provide you with a quote.
Alternatively, if you haven’t already done so and been directed here by a quote reply, please go to https://www.clickmechanic.com/mir-requests/quote-missing
FAQ’s
Can I supply my own parts?
No, we will not fit customer supplied parts unless they are a brand new item, purchased from a dealership with the receipt as proof of purchase. There is no flexibility over this due to insurance and warranty issues.
What happens if the mechanic finds that a NOx sensor doesn’t require replacing?
In this scenario, the mechanic will provide a no obligation quote for the correct repair. Should you accept this, the mechanic can alter the booking accordingly. If you decide not to go ahead with the alternative repair, the mechanic can change the booking to a diagnostic booking and charge according to the time spent with the vehicle.
Is a NOx sensor the same as a Knock sensor?
No, a knock sensor is on the engine to monitor for poor combustion and ignition advance AKA pinking) via vibration