Purge valve stuck open


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P0420 is usually a cat failure. When the o2 sensors aren't working properly it will usually set an o2 not switching code or a stuck rich/stuck lean code. If its wiring it would throw a circuit high /circuit low code. The p0420 means that the o2 sensors are indicating there is not enough change in the oxygen concentration between the pre and post cat sensors indicating the catalyst isnt operating at its proper efficiency.

The guy above who said purge valve stuck open, that would not cause a p0420, it could cause a lean or rich reading of the upstream o2 sensors. But would usually throw an evap code for a large leak.

 

Also, being a 2016.... what state do you live in? I know in PA, CA and other "california emissions" states there is a law that forces manufacturers to cover emissions related failures for 10 years and either 80 or 100k miles iirc

 

navada

 

Check your book for warranty, I don't think it is only Ca anymore, could be a long federal one on Cats too.

The easiest way to diagnose a bad cat is to run it at a high idle when warmed up, look at the O2s with a scan tool. The front (sensor 1) should pulse up and down in voltage, the rear (sensor 2) should stay steady at around .3 or .4 IIRC, steady for sure anyway. If the rear follows the front up and down the cat isn't working.

Again double check the warranty in the book, look for emissions and/or cat converter warranty, don't trust the dealer to tell you. Cats are expensive.

 

was the upstream 02 sensor switching Correctly & you say you bought engine coolant temp sensor what was the Temp reading if its over 190 the sensor is OK or are you tiring to diagnose the problem without a scan tool .

 

I have a 97 Toyota Tacoma, 2.4 liter, 4 cylinder. Every few years the truck gives the P0420 code. I have an aftermarket exhaust header. The flange that connects the header to the catalytic converter does not have an recessed seat for the gasket and the angle is slightly off. The catalytic converter flanges have a recessed area for the gaskets to sit in. The gasket burns out and starts to develop an exhaust leak at the bottom of the header flange. I received an early model header that didn't have the recessed flange. Anyway, I replace the burned out gasket with a new one and the P0420 code goes away until the next gasket goes. Is there any possibility that you may have an exhaust leak?