The engine emissions and AWD warnings started illuminating intermittently. A scan of the DTC codes produced 0172 (bank 1 fuel too rich) and U0401 (fuel system abnormalities A/T). The codes went away for a couple months, then returned and stayed on. Internet searches found that the fuel injectors were potentially clogged. This engine uses direct injection instead of intake injection, so the injectors spray fuel directly in the cylinder next to the spark plug. This requires very high pressure and the tip of the injector is directly exposed to the burning fuel. Additionally, the intake valves are not washed by incoming fuel so they can get dirtier.

I decided to increase the cylinder temperature by switching from premium to lower octane fuel. Plus, I added Techron injector cleaner every fill up. After four complete tanks of this mixture, the warning lights went off and finally stayed off—For 400 miles so far. We were able to pass the yearly emissions test. I will use mid or low obtain fuel and occasionally add injector cleaner and see if that works. If not, I will change out the six injectors. Considering the mileage, I’m surprised at these potentially expensive problems.

I purchased my 2016 Honda Pilot brand new. During the first year I had an emission control light come on and the dealership told me it was my software that needed to be updated which supposedly was the problem or so I thought at the time and now I'm beginning to wonder if they just turned the warning light off and never fixed the real issue. My warranty expired in Sept 2019 and I only have 31000 miles on my Honda Pilot; and on a recent trip from Oklahoma to Alabama, the emission control light came on again!

Of course the owner's manual is not much help with this type of warning light and so I went to the internet to do research. It appears this problem exists on many 2016 Honda Pilots but Honda has never done a recall. Now I'm angry that it could be a costly replacement of the fuel injectors and this has been a common problem with this new fuel injection engine and now my 3 year or 30,000 mile so-called warranty has expired! This is BS! Do we have any cars that are made in America anymore?

It took a total of 4 different trips to the dealer to attempt to fix the check engine light.

1st trip - dealer just reset light and said try that.

2nd trip - 4 days later check engine light came in again, they check intake manifold gasket, it was ok, reset light and on my way. Dealer had car for 2 days.

3rd trip - 7 days later check engine light came in again, this time oxygen sensor replaced and sent on my way. Dealer had car for 3 days

4th trip - check engine light came in again in about 7 days. this time dealer kept car for 11 days trying to figure it out with engineers in California. Dealer replaced fuel injectors, drove vehicle, light came back on. Then they replaced some ECU of some sort (computer brain box). Drove vehicle for 200 miles, called it good.

Had car for 4 days now, check engine light still off. I'm not waiting for more crap to go bad. Another post explains my car not starting at all last December. Another post explains the Auto Stop/Start intermittently working with dealer having no clue how to fix. 32 years of buying Hondas down the tubes. Trading it in soon for a new Highlander.