Fuel Too Leak (Bank 2)

As it has come on before for the same code then went away I might look at an injector flow test, one might be dirty or sticking, or it might be that bank one is running rich and the ECU thinks that means B2 is running lean. You might look at the fuel trims with a scan tool to see what they are doing, if it is adding fuel on B2 and B1 is normal then I would check for leakage, just spray around the plenum and manifold with starting fluid and see if anything changes. Check the EVAP purge as well, The hoses can come off and then you get a vacuum leak when it triggers the purge on.

I did a live data scan of the fuel trim with my FIXD scanner, didn’t even know I could do that, but here the average numbers. Not sure if that helps you at all

They might except they don't show up. Do you see anything other than a logo on your end?

Short-Term Fuel Trim (STFT):
Bank 1 = 0 % to -1.6 %
Bank 2 = +16 % to +18 %

Long-Term Fuel Trim (LTFT):
Bank 1 = -0.8 % to 0 %
Bank 2 = +12.5 % to +13.3 %

And yes, I only see logos

Thanks for the response on the images. Those numbers are showing it adding fuel. Try this watch them and then rev the engine up to 2500-3000 and hold it there for a bit. If the bank 2 starts to go down then you have a vacuum leak somewhere that is letting in air after the MAF

I actually already did that test, held the RPM at 2500 for 10-15 seconds, numbers looked very similar, STFT for Bank 2 stayed between +16% and +18%, LTFT was around +12% and +13%, Bank 1 remained around zero the whole time. Would this narrow it down to fuel injectors or purge valve? Maybe a gasket that didn’t properly seal or bolts that need to be torqued down more?

OK if it stayed the same at higher rpm it probably isn't an air leak. What voltages are you able to see from the O2 sensor with the scan tool? Have you swapped the upstream sensor just to see if it has an issue?

Got it. So I actually did run a live data voltage test for the O2 sensors, the downstream O2 was hovering between 0.09V and 0.72V. My scanner couldn’t read Sensor 1 (it showed as “unsupported” in the scanner app). I haven’t swapped the upstream sensors yet, but I can check if they’re interchangeable to rule that out

My question is, would it be normal for it to be a sensor issue right after a gasket replacement job? Especially if I never had any issues with them to begin with and I didn’t disconnect them either in the job

Would depend on what you might have hit by accident while working. There might be a wire that was hit or a bad connection and it was disturbed during the work. Or a piece of gasket might have gone through and blocked some of the sensor. Are you getting a single notification in your email or multiple updates?

A test I just tried now (as many users had mentioned online) was to spray carb cleaner along the intake manifold, throttle body and plenum and valve cover gasket areas, hoses surrounding the area as well but I didn’t see any spikes or changes in my RPMs

Figured that would be the case. The earlier rev up while watching the trim indicated that there was no unmetered air like a vacuum leak. It is an easier test done from the drivers seat than doing the spray method. You don't have an exhaust leak on that side that might let air in near the sensor?

How could I check that? Do you think I should replace the O2 sensor on that front side of the engine?

If you don't hear a leak it's likely not the problem, a leak at or lust after the converter can let in enough air that it will read lean and dump in fuel. As for the sensor, compare the voltages between both sides, Shut the engine off and look at the base voltage on a cold engine, they should be the same. Now start the engine and watch as they change, it should take a minute for it to go into closed loop, if the voltages are close then the sensor is probably OK and you have a different problem. That will take testing the rest of the fuel system, Fuel pressure and flow testing the injectors.

I’m not sure if I am up for all these tests if I’m being honest, I just ordered a new O2 sensor to replace that upstream sensor in bank 2, a new purge valve solenoid and a new PCV valve. Do you think it’s a good idea to replace all those?

I also ran some seafoam in my gas tank for the first time last week, this was after the valve cover gasket job

Don't replace them all at once. Especially these days when it seems every third part is bad right out of the box. If you clear the codes, how long does it take for it to return? did it get worse after the VC gaskets? If yes then look over the engine real close, pinched wire, loose connection, even a bad ground can change what the ECU "sees" from the sensors and cause problems.

I’d say it takes about two days or so for it to come back up, it’s definitely more than a day in between. This last time, it went away on its own which it’s done before. The time before that I turned it off and it stayed off for a couple days on the dash but it still comes up as a stored code when I scan it.

And it’s the same pattern of codes coming on and off since the valve cover gasket replacements, not better or worse

CEL is off at the moment, I scanned it to be sure and no codes came up

One more thing, I ran some live data tests once again today after the car had sat for a few hours. On cold start idle, the short term fuel trims were around +7.8% on Bank 1 and +26.6% on Bank 2, with long term trims at 1/6% (B1) and +6.3% (B2). Then, when I revved the engine to around 3,000 RPM while parked, both short term trims stabilized at 0.0% and the long terms held steady -1.6% (B1) and +7.0% (B2). Seems like Bank 2's short term correction disappears once RPMs increase, which makes me think the Bank 2 upstream O2 sensor is slow or biased when cold, since the ECU no longer adds extra fuel under load. Thoughts?

In the case of it being cold, the ECU isn't controlling the fuel yet, it just uses a simple table to add fuel, once it heats up and the O2 sensors start operating then it will go into closed loop and you will see the numbers change as the ECU starts using feedback from the sensors to control the fuel mix. Take a look at the O2 mv readings and run it up to about 3000 rpms and see if you read 800 mv or so with it wide open. That should at least tell you if the O2 is responding within range as the ECU should go open loop at WOT. If you see something different then the sensor is likely faulty.

Got it, this is very helpful information, thank you! So just to clarify, start the car up, let it idle for several minutes to get the engine hot and the temp gauge to the center, then do those readings? Both at idle and at the revved 3000 RPMs? My sensor does live data for the O2 sensor voltages, that's what we want, correct?

You have it. The open loop while cold just show that the sensors are there, then you can watch as they start reporting, if bank one starts reporting in say 20 seconds but bank two takes a minute that would tell you that it has a problem, but not what the problem is. Then once it warms up watch both sensor one voltages for both banks. The images are still wonky so that would make it harder, but if your tool allows you to capture the results you could create a video for later. However watch both sensors at WOT, if they are close to the same voltages the system is reading them correctly and we need to look for a different problem. BUT if you have ordered the parts, you might change out the sensor, just to see how it reports. Also you might want to clear the systems learned values, some scan tools will let you do that in the special tests. That resets things like base idle, fuel trims go to zero and timing resets. Then you start there and see what it does. If you warm it up and still have the system adding fuel then it's time to clamp off all vacuum lines, I have seen bad brake boosters and other vacuum items leak, generally they cause a problem on both banks though. Same with fuel pressure, both sides are fed the same so it likely isn't a bad pump. Ignition is the same, plus an engine misfire would be noticed. Being this is on only one bank it is something else.

Thank you so much, that explanation helped a ton. I ordered an OBDLink MX+ that will be here later today so I can pull live data from all O2 sensors. My FIXD scanner didn't give me the option to read the other sensors, only one, so fingers crossed this new one will actually let me see what Bank 2 is doing. I will report back once I have that data because I really just want to be sure already, I've never taken my car for this long of a road trip but I'm also always constantly on top of my maintenance like a maniac with it

We'll be here and hopefully fully operational when you have the data.

OH if you want some fun on a similar situation my friend Paul just did an interesting case showing the testing I'm suggesting, looking at the trims and then a flow test. So you might find them interesting as well.

https://www.youtube.com/watch?v=J4-5eAsbgCw
https://www.youtube.com/watch?v=iguLgNhavAs
https://www.youtube.com/watch?v=RuCDEpLZH0g

Thank you, I’ll be performing the live data tests soon here. Hey Steve, do you happen to have an email or another form of contact? I’ve been wanting to send you screenshots of those tests (fuel trim, sensor voltages, etc.) but the site doesn’t seem to let me

Alright, finally performed the live data tests with this new fancy scanner, here are the results:

At idle (fully warm)
Bank 1 LTFT: +1.6%
Bank 1 STFT: +7%
Bank 2 LTFT: +15 to16%
Bank 2 STFT: +25-30%
O2 sensors both cycling from ~0.1 to 0.8V

Revved at ~3000 RPM
Bank 1 LTFT: +1.6%
Bank 1 STFT: ~+7%
Bank 2 LTFT: +15 to 16%
Bank 2 STFT: ~0%
O2 sensors still both cycling from ~0.1 to 0.8V

Another detail I’ve noticed while driving is that when coming to a stop at a light, then hitting the gas on green, the engine may stumble or hesitate. Not all the time but it does happen sometimes

Yep, it looks like you have an injector that is leaking or you have a catalytic converter that is partially clogged, I would remove the spark plugs on bank two and look at them, you are looking for the one, (or all) that are dark in color. This will be the cylinder that is leaking, also you could have low compression on that cylinder as well. Here is a guide to help check the converter on bank 2

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please go over this guide and get back to us and let us know what you find.

Just to be sure, Bank 2 is the front of my specific engine and cylinders 4, 5, and 6 would be at the front, right? In that case, I will check all of the coils and plugs there. Since you mention this, my concern now is the low compression you mention. Back in July of this year, I had a misfire code on cylinder 4 and it turned out there was zero compression on that cylinder. That job costed me $1,800 for a cylinder head replacement, timing chain and water pump as well. Should I be concerned? My road trip to Cali is in three days from now

Also, just as an FYI, I replaced the MAF sensor, intake hose boot (accordion looking one), purge valve solenoid and PCV valve, all with Honda OEM parts

Quick update, after those replacements, I went ahead and ran the same live data tests once again. At idle, Bank 1 STFT stayed around 0 to -1.6% with LTFT +5/5% to -2.3%, while Bank 2 STFT ranged 15-18.8% and LTFT +8.6 to +20.3%. At 3,000 RPM, Bank 1 STFT -4.7% to -1.6%, LTFT -2.3%, and Bank 2 STFT 6.3-10.2%, LTFT +9.4%. O2 sensors on both cycled normally between 0.1-0.8 V. Fuel trims on Bank 2 seemed to drop at the higher RPM, so it seems like the lean condition eases under load somewhat

Yes, bank 2 is on the left side of the engine, closest to the front of the car. Let me know what you find.

New update! So the CEL just came back on yesterday, after being off since 12/28/25, this is the longest it’s gone before turning back on so I thought the problem was gone for good. Just to refresh you, ever since the valve cover gasket job back in late October last year, I’ve replaced the MAF sensor, the purge valve, PCV valve and intake hose/boot. I also put some Seafoam in the fuel tank around November. There are no noticeable issues with the engine such as rough idling or trouble starting, nothing like that, in my opinion it’s operating perfectly. I also checked live trim readings today while idle, Bank 1 showed STFT around +2.3% and LTFT about -0.8%. Bank 2 read STFT around +25.8% and LTFT around +12.5%. I then revved it to around 2,000rpm, and Bank 2 STFT dropped to around +10.9% while LTFT stayed around +14.1%. Bank 1 STFT about -5.5% and LTFT around 0%. What do you guess it could be based on this information?

Those numbers and the reaction to the engine rpm now with the bank 2 coming down as opposed to staying the same says you have an air leak on bank 2 or there is an overachieving injector on bank 1 that is causing the PCM to try to balance it, put I would look at the leak first. Pull the pcv and block it off, what do the trims do? It's possible that one of the valve cover gaskets is letting air in, that would bypass the PCV system and the MAF. I would expect a leak there though to affect both sides. Could also be an intake gasket.