How to

How to check a NOx sensor

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A vehicle’s NOx sensor is one of the most complex pieces of kit you’ll come across. They’re tricky to test and difficult to diagnose. But in a few simple steps you’ll be able to pinpoint potential issues with a quick NOx sensor check. 

Find out if a vehicle’s NOx sensor is the cause of engine issues with some pointers from the Delphi experts. Watch our video to discover: 

  • What to look for on the wiring diagram 

  • Which tests to perform for a quick diagnosis 

  • How to operate the diagnostic tools you’ll need

Sensors Vehicle Electronics & Engine Management How to Technicians 1 min read

How often do NOx sensors go bad? 

NOx sensors don’t have an expected lifespan, as each individual vehicle and set of driving conditions can have different effects on the performance of the sensor. However, a NOx sensor is a relatively delicate piece of kit, which means it may need attention at some point. 

Can you repair a NOx sensor? 

NOx sensors cannot be repaired as they are a complex component, with multiple measurement chambers. For NOx sensors you must diagnose, test, and replace. 

Can a NOx sensor be cleaned?  

We would not recommend cleaning the NOx sensor due to its sensitivity. Replacing a NOx sensor would be the preferred course of action if dirt is clogging up the sensor. 

Can I drive with a bad/faulty NOx sensor?

No. A faulty NOx sensor may prevent the engine from maintaining its emission standards at an acceptable level, or in more extreme circumstances prevent the engine from starting at all. With a bad NOx sensor the vehicle is likely to go into Limp Mode, which should indicate there’s an issue with the engine to be addressed as soon as possible. 

Is a NOx sensor the same as a lambda sensor? 

No, the two components are not the same. A NOx sensor is used to measure the levels of oxides of nitrogen being emitted, while the lambda sensor is used to measure the amount of oxygen present in the exhaust gas.


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