I have a 2017 Kia optima hybrid, it has about 115k miles on it. I’ve been having trouble with it lately. The car lost all power once and I took it to the dealer they told me it’s the knock sensor, so I had it replaced. 1 year later it goes out again, but this time they are saying it’s because of the catalytic converter. I did get a P0420 code on it, but the car gave out before I can take it to the dealer to get checked out. My question is can a bad catalytic converter damage the knock sensor?
My question is can a bad catalytic converter damage the knock sensor?
Of course not.
The catalytic converter might not even be bad, many things can cause the P0420 code. You'd be better off staying away from the dealer and finding a good independent mechanic.
a bad cat cannot damage the sensor, but it might cause engine knock/ping.
The knock sensor is a fairly primitive and mechanically robust device which seldom breaks in itself. Frankly, Ive never seen a malfunctioning knock sensor in my 30+ years of driving and car DIYing experience. That such a reliable device breaks down two times in a row would for me be a reason to look for a malfunction outside of the sensor itself. First of all I would check one of the two things:
1) Is it /was it mechanically tigtened properly against the engine? If not (if an incorrectly tigtened sensor loosened itself with time due to engine vibrations), engine detonation sounds might be unable to reach the sensor´s built-in "ear" properly, giving the ECU all reasons to complain about this sensor malfunctioning. In case of doubt just loosen the sensor and then retighten it with a torque wrench and exactly with the by-the-specs torque. AFAIK it is just one single screw and a 5 minuites job.
2) What error codes were the reason for the mechanics to replace the knock sensor? What error codes does your ECU have now? Many of knock sensor-related error codes might mean not directly issues with the sensor itself but rather sensor wiring-related problems. Check the sensor connector, make sure the contacts look good and shiny, in case of doubt use contact cleaning spray. Visually inspect the sensor wiring itself.
All the above is based on the presumption that you used a quality part for the sensor replacement. In case of chinese junk, it might well be the new sensor itself.
As to the P0420 code you mentioned, I am afraid that in most cases it is a fairly solid indicator that your cat converter is dying. In theory, this code could have many reasons, but in real life it is usually the cat itself, sorry. What this code virtually says is that the signal of your after-cat O2 sensor is electrically OK, but on the logical level is mimicking that of your pre-cat sensor closely enough, which is impossible as long as the cat converter (which is in-between the two sensors) is doing its job properly.
Is your car burning oil? That is a frequent reason for cat problems. Then an attempt to first clean the cat may be worthwhile, although success chances are not very high. Or maybe it is just age - got word that some of the modern cat converters are cheaply made.
To be honest I can’t remember what code came out. The car loses all power and the dashboard lights up with all the lights. The dealer told me the code that keeps showing up has to do with the knock sensor. The car doesn’t really burn oil at all.