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Code p0420 Catalyst...
 
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Code p0420 Catalyst efficiency below threshold bank 1

  

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Hi, Scotty hope you are doing well? I wanted to ask you about the problem I have in my car. Its a toyota yaris sr 2008 1.3 petrol UK model. When I brought the car I didn't drive it and it was sitting in my drive way for a month. Because I didn't had an insurance so after a month I got an insurance and started driving it. After one week of driving I got an engine light so I toke it to the mechanic and checked the car diagnostic system it was showing that the catalytic converter was not good. So I chnage the while exhaust including the catalytic converter. But the light still didn't disappear. Yesterday I ordered a car diagnostic checker and I checked the engine light to see what was the problem. It was showing me that catalyst efficiency below threshold bank 1. So I toke it back to the same guy because when he changed the whole exhaust including catalytic converter it was on warranty so he changed it again yesterday including the sensors but the light is still on and it showing the same problem catalyst efficiency below threshold bank1. I put some catalytic cleaner in the tank and toke it for a drive on highway for about 1 hour and 30 minutes. It still didn't help. Can you help me please thanks!


When you say ‘whole exhaust’ can you clarify exactly what was changed?


When I say whole exhaust I mean the exhaust and catalytic converter was changed.


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See here for other causes and troubleshooting:

https://www.obd-codes.com/p0420


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