Not sure why you need to replace all the sensors but see below. Make sure to use Honda parts.

 

Before you replace those, let’s talk. Do you have engine codes you’re trying to solve? Your money may be better spent on something else. What year model, trim level and mileage?

 

Thanks. Yeah man. 2017 Honda Pilot Touring AWD. Emissions light constantly on. Honda already replace all the fuel injectors under warranty. Then 3 months later, lights came back. At that point no longer in warranty. I don’t know how to tell which O2 sensor is bad or if it’s the cats?

 

Milage?
Ok, yes, there are various things that can cause an emission light to come on. It’d be good to get the engine codes by plugging in an OBD II scanner. These are relatively inexpensive, a little more for one that does more, or stop by a major auto parts store, most will scan your vehicle for free. After getting codes, post them here.

For some advice on these 3rd gen Pilots, It is critical to be strict with changing the oil every 5,000 miles using a quality full synthetic 0w-20 engine oil (no semi synthetic or extended performance oil). Older used oil will begin to travel up into the intake and exhaust manifold. This can cause fuel injector and emissions issues. Use top tier fuel such as Chevron, Shell, Exxon, Mobil. As the fuel additives will help keep the engine clean. Air/fuel mixture can be effected by a dirty air filter, and I would suggest cleaning the Mass Airflow sensor to ensure a proper reading. This is done by removing the sensor, holding it in the orientation that it is installed, spray a few short burst of MAF or Electronic Cleaner directly into the visible electrodes in the bottom (avoid getting cleaner in the upper covered portion). Let condensation dry completely before reinstalling.
I’d also would purchase a VCM disabling device such as S-VCM or VCM Tuner II, to keep the engine running on all 6 cylinders 100% of the time. This will prevent a lot of engine and transmission issues.