Nissan Micra K13 Engine Code: P0420

[AlgonemaCreta]

Nissan Micra K13 engine code advice for upcoming MOT

Engine Code: P0420 Catalyst system efficiency below threshold bank 1

Any idea about easy fix for this? It comes on and then sometimes goes off by itself, otherwise I can clear the code and it will stay off for a period of time.

Probably need to get this sorted for my MOT next month. Any advice appreciated

 

[SplanK]

A handful of reasons for this code, just a few of the top of my head

1. Bad sensor. There are 2 sensors which read the exhaust to determine of the cat is functioning. If one of them has gone bad, or the wiring or connector is bad then it will flag up a code. The sensor could also be contaminated and thus not reading correctly.

2. Bad cat. The cat convert may have expired. Usually they last a long time but there are a number of reasons why the life could be shorted

3. Bad exhaust. You could have a hole in the exhaust somewhere which could result in skewed results.

What is the overall condition of the engine/how many miles? There is no magic 'reset the ECM' cure for this and the fault is likely something needs repairing somewhere.

If you are able to, check the condition of the exhaust and immediate wiring to the sensor.

You maybe able to check the sensor by checking live data using your scan tool, or checking the sensors resistance but that in itself may not give you a solid answer, without knowing exactly what you should be looking for in terms of values.

Ultimately you may need to take the car to a respectable garage to diagnose the issue correctly rather than guessing by say replacing the sensor (aka parts cannon) and see what happens.

 

[AlgonemaCreta]

A handful of reasons for this code, just a few of the top of my head

1. Bad sensor. There are 2 sensors which read the exhaust to determine of the cat is functioning. If one of them has gone bad, or the wiring or connector is bad then it will flag up a code. The sensor could also be contaminated and thus not reading correctly.

2. Bad cat. The cat convert may have expired. Usually they last a long time but there are a number of reasons why the life could be shorted

3. Bad exhaust. You could have a hole in the exhaust somewhere which could result in skewed results.

What is the overall condition of the engine/how many miles? There is no magic 'reset the ECM' cure for this and the fault is likely something needs repairing somewhere.

If you are able to, check the condition of the exhaust and immediate wiring to the sensor.

You maybe able to check the sensor by checking live data using your scan tool, or checking the sensors resistance but that in itself may not give you a solid answer, without knowing exactly what you should be looking for in terms of values.

Ultimately you may need to take the car to a respectable garage to diagnose the issue correctly rather than guessing by say replacing the sensor (aka parts cannon) and see what happens.

really appreciate your comment - car has been well looked after, but it has now just turned over 100k miles, so I guess cat replacement sounds obvious casue.

Will pop it over to the garage later

 

[SC2929]

MIne just came on as well
check engine light
OBD2 reader says P0420

Prior to that, car has been running fine for the last 2 months since I got it (and passed MOT last week and emmsiisons fine), and is a great little vehicle.
Light came on today during return from local town
Still running fine.
Have cleared the code and will see if it comes back.

UPDATE: So far so good, and hopefully was a one-off or occasional misreading.