[theechasequinn]

I've had problems out of my car for about the past month now. Beginning with the P0420 catalytic system/converter below threshold for about a month. I had the bank "B" converter replaced back in May of last year (I think that's what they referred to it as.) and have not had any problems until the light came on about a month ago. The light will come on for a day or two then go off like nothing happened.

Earlier this week driving home from work I got off the interstate and noticed my car sounded like what I can only describe as a pissed off lawn mower. While driving to have the code read I also noticed the "eco" mode would not engage. After having a code reader put on the car in addition to the P0420 code was a P3400 code. After having the car combed over by a shop I trust they advised me to have the "Rocker Arm Oil Pressure Switches on the valve cover" replaced, 2 $30 parts so I was hopeful this would fix the issue and there would be no more problems. Had the parts put on, computer cleared. I expected the catalytic code to come back since I'm still waiting for the converter to come in to be replaced, but it began doing the exact same thing as a few nights before, horrendous sound and no eco tec.

If it makes a difference to not or not, I've checked the oil quite a few times over the past few days and from the best I can tell, none has been lost nor am I noticing any leaks when I park the car.

Brief maintenance history of the car if it matters.

Plugs were replaced with Bosch (which I feel has contributed to the screw ups) in February of 2015. Was not advised these were the wrong plugs until October of 2015 when I had them replaced with NGK. These plugs were roughly in from 71,000 miles until about 82,000.

Water pump and timing chain were replaced at 80,000

Routine oil changes every 4-5k with Royal Purple 5W-20 since buying the car with 60k (car currently has right under 110k)

Sorry for the excessive information but I'm just stumped at the moment and not sure what other direction to go.

 

[Miker]

P3400 is related to the VCM deactivation. The "Rocker Arm Oil Pressure Switches on the valve cover" (spool valve) they replaced might have been the cause except that you have the same problem.

The VCM needs to have the MAF (Masss Air Flow) and TPS (Throttle position Sensor) all within the proper operation range.

Have you ever cleaned the MAF? or do 8th gens have a MAP ? Either one needs to operating correctly.

It also may be the coolant temperature sensor. I say this because you may have read that some folks are disabling the VCM on 9th gens by fooling the coolant temperature sensor to react as if the coolant isn't up to temp.

How's your coolant level?

Some causes for poorly operating VCM are low oil level, bad MAP, bad MAF, bad TPS, low oil pressure, dirty oil passages ('cept your OCI looks like that's not the case)

Check for a faulty EOP (engine oil pressure) sensor. Could be reading incorrectly thus not allowing the ECM to activate the deactivation system. (wow!)

 

[theechasequinn]

P3400 is related to the VCM deactivation. The "Rocker Arm Oil Pressure Switches on the valve cover" (spool valve) they replaced might have been the cause except that you have the same problem.

The VCM needs to have the MAF (Masss Air Flow) and TPS (Throttle position Sensor) all within the proper operation range.

Have you ever cleaned the MAF? or do 8th gens have a MAP ? Either one needs to operating correctly.

It also may be the coolant temperature sensor. I say this because you may have read that some folks are disabling the VCM on 9th gens by fooling the coolant temperature sensor to react as if the coolant isn't up to temp.

How's your coolant level?

The particular description that appeared with the P3400 code when I had the scanner put on was "Cylinder Deactivation Bank 1" Which is foreign to me either way unfortunately. I'm uncertain on MAF/MAP. As far as the coolant level, it appeared to be normal when checked a few days ago when assessing the problem and being under the impression it was the "rocker arm oil pressure switches." I'll continue to assess the problem using the pointers you listed, I greatly appreciate it.

Thankfully it's still running normal, well I saw normal in terms of when coil packs have went bad in the past during the time I've owned it.

 

[Miker]

The particular description that appeared with the P3400 code when I had the scanner put on was "Cylinder Deactivation Bank 1" Which is foreign to me either way unfortunately. I'm uncertain on MAF/MAP. As far as the coolant level, it appeared to be normal when checked a few days ago when assessing the problem and being under the impression it was the "rocker arm oil pressure switches." I'll continue to assess the problem using the pointers you listed, I greatly appreciate it.

Thankfully it's still running normal, well I saw normal in terms of when coil packs have went bad in the past during the time I've owned it.

I added a few more things to look at in my post. Check it out.

 

[anyday901]

I had the p3400 code on my 2010 accord 2dr v6 ex-l. For me it was the rocker arm oil pressure switch on the front left side under the engine cover. Got the part from Honda cheap and installed it problem went away. If you don't get it taken care of it gets worse. I had it cause a misfire and my engine light started blinking on me. But after I replaced sensor as was good.

Sincerely,
Anyday901

 

[sidlish]

I have the same car and it's likely the start of a MUCH worse issue. Google "Accord V6 8th Class Action Lawsuit" or "Accord V6 8th cylinder 3" and read up. Long story short, the whole VCM / Eco design in the 8th gens is super screwed up. It dumps fuel into the non-operating cylinders (eco mode = when the V6 drops down to V4) and doesn't ignite it. That rots the piston rings, lets oil into the spark plugs, etc. This eventually turns into burning a lot of oil and spark plugs (namely in cylinder 3) dying in less than every 3,000 miles (and mine seems to be getting steadily worse), blowing catalytic converters, etc. The solution (to kick the can down the road quite a ways) is a $3000 piston ring job. It sounds like everyone commenting on this post was also NOT notified about the class action lawsuit which is now over unless you bought your car around this time in 2012 or later. It has an 8 year from date of purchase effective span. Love Hondas in general but the ~08-12 V6 stuff is absolute crap. Some vehicles for whatever reason it never becomes an issue. For me, mine's got more recommended repairs than it's value (of course, half of the repairs are dealer BS stuff that doesn't need to be repaired).