Hey! Anybody know the part number for the o2 sensor (bank 1) that generates the p0420 error code? I have the dreaded light on the dash, using the dongle it gave me that error code, can't afford a new cat so I would like to try changing the o2 sensor first and hoping that fixes it. Thanks!
Good luck with that. P0420 does not mean the O₂ sensor is bad (or that A/F sensor is bad, for that matter). Replacing it/them seldom fixes a P0420 code. Your first order of business should be to run through the engine parameters (short and long-term fuel trims, for one, misfires on any cylinder, etc) and check they are within spec. A poorly running engine will impact the catalytic converter's efficiency.
Brand of your dongle for reading codes? Program on the phone + dongle? Not all adapters work correctly. What parameters can your device show besides the error code?
It's generally not the case that either of the bank 1 O₂ sensors 'generates' the P0420 code. (We don't really have to keep saying 'bank 1' as the engine is an inline-four so there's only one bank.) The P0420 code is reported by a self-test routine that the ECM can't even run unless it thinks both O₂ sensors are ok. The outcome of the test depends on readings from both of them, in ways that would be hard for a malfunctioning sensor to simulate. In other words, I'd say it's usually wishful thinking to hope that a P0420 code is going to turn out to mean something besides what it actually means.
it's a very common practice among mechanics/shops to blame the messenger (i.e. replace the O2 sensor) without any further diagnosis.. If you get p0420/p0430 chances (99% of the time) are the sensors are working and doing their job.
I think that is a little beyond my knowledge and skills, is there a thread that I can read up on this (or a link /video)? I'm using the Autel AP200 that was recommended in another thread on this forum. So, the cat is bad?
Not necessarily. A poorly running engine could affect the efficiency of the cat in doing its job. If the engine is running well and sensors indicate that they are within spec, and there are no exhaust leaks upstream of the cat, then it could be that the cat is worn out. But you have got to do the work before you can make a decision.
Engine is running fine, no misfires or anything, a very smooth ride. According to the Autel, the only problem is the p0420 error, no exhaust leaks that I know of but I have not checked...
Autel AP200 can generate a report in pdf format. You can attach this error report to your messages. Data on engine operating parameters at the time of this error is required, they can provide more explanations than just the lamp lighting up.
In one of your earlier threads concerning the P0420 code, this was one of the replies on September 27, 2024,
cat doesn't meet the efficiency numbers required by the ECM, not sure what that magic number is. It could be just below 1% of the minimum requirement. Depending on how strict the emission inspection in your area, the check engine light can be suppressed by just putting in a spacer in your O2 sensor. Normally the cat degrades over time due to oil burning or been driving with overly rich or lean conditions. A bad cat will not let the car accelerate (worst even move) and you'll hear marbles in your exhaust (clogged)
I'll attach it the next time I use the Autel, should be this weekend I understand this a little bit better now, I didn't quite understand this at the time, it does not seem to be burning oil at an accelerated rate. It failed inspection becuase of the engine light on and the error code (plus brakes (back brakes and parking), but that's another thread). I bought one of these , it arrives from Amazon on the 27th: If I can get away with using that even for a year or (drops to knees and prays) two, that would make me as happy as the first time I tasted Ice cream!
Awesome! Attaching the files that I got from the Autel... not sure if I did this right, let me know if I f'ed up and will try again if need be.
The report has been received, there are errors. P0420 catalytic converter error. Three errors indicate that there is a historical error, a current error, and a рending error. These may be problems with the catalytic converter itself, which has lost its efficiency, or other malfunctions in the formation of the fuel-air mixture, which means fuel supply malfunctions, air leaks, and much more. The problem needs to be addressed, but it has little effect on the car's driving, but you may not pass a technical inspection if you have exhaust gas toxicity measurements taken. C2300 ACT SYSTEM MALFUNCTION. The transmission control ECU outputs this DTC when it detects a malfunction in the shift control actuator assy system. For this code, see the manual. C2318 Low voltage was detected at some point in time. For example, when starting the car. This may indicate a discharged 12V battery. B1421 This error can be ignored altogether, the light sensor is not illuminated by sufficiently bright light
