Check engine light with P0420 code - catalyst efficiency problem, what should i do?

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Check engine light with P0420 code - catalyst efficiency problem, what should i do?

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  • Last Post 3 days ago
wodapod103 posted this 3 weeks ago

My Check Engine Light came on recently, and when I scanned the car, I got a P0420 code. From what I understand, it means the catalytic converter isn’t working efficiently. The car seems to run okay - no big loss of power or strange noises - but I’m worried this might get worse. Has anyone dealt with this before? What are the typical causes, and can I keep driving like this for a while?

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liwix97028 posted this 3 weeks ago

P0420 is pretty common once your car has some mileage. Usually, it’s either the catalytic converter wearing out or the oxygen sensors acting up. Since your car drives normally, you can probably keep driving for a bit, but don’t wait too long. Check for exhaust leaks too - sometimes a hole or bad gasket before the cat can cause this code. InCarDoc is good for reading codes, but it won’t do advanced tests on sensors or the cat itself. If you want to DIY, clean or replace the oxygen sensors first - they’re cheaper than a new cat. But eventually, the catalytic converter may need replacing.

jafegox333 posted this 3 weeks ago

P0420 means your catalytic converter efficiency is below threshold, often Bank 1. Causes can be: worn-out or damaged catalytic converter, faulty downstream oxygen sensor, exhaust leaks before the sensor, engine running too rich or too lean - check for other codes. You can use InCarDoc to check codes, but for proper diagnosis, a shop with advanced diagnostics is best. Driving with a bad cat won’t damage your engine immediately, but it may increase emissions and cause failed emissions tests.

natika1316 posted this 3 weeks ago

I had P0420 last year on my Honda. The cat was almost dead, but I didn’t notice much difference in driving. I replaced the oxygen sensor first because it was cheaper, and the code didn’t come back for a while. Using InCarDoc helped me see when the code popped up again. Definitely get a good scan before spending on parts.

xatah88954 posted this 3 days ago

Yeah, I’ve been through this. P0420 popped up on my Tiguan, and I used InCarDoc to pull the code. Car was driving fine, like yours, but still had that annoying CEL.

Turned out the rear O2 sensor was a bit slow - not totally dead, just sluggish. I changed it and the code went away. Try checking your sensor data in InCarDoc - could save you from replacing the cat for no reason.

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