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I have a 2015 Pilot and a couple weeks ago my check engine light came on and a few days later it went off on its own. I scanned it after it went off and up came codes P0172 and P0175, bank 1 and 2 running rich. She was running smooth, no skips no beats so I wasn't too worried about it. I had to take it into the dealer for the air bag so figured I mention the CEL then so I did and I also mentioned I had the extended warranty and so they scanned it. They told me it was running rich and that I needed new fuel injectors. Anyone have this experience before? The CEL went off on its own and seems to be running fine. Not sure if it really needs injectors or if dealer is trying to make money. They cleared the codes so I cannot take it for a 2nd opinion.

I should mention that 2 years ago around this time of year I got the check gas cap light and a couple weeks later I noticed my air filter had a bit of fuel on it but since then nothing and she runs mint. Only has 18k.

Weird that both banks are running rich I would expect one bank to run rich if it was a faulty injector.

Any thoughts, experience's or opinions?

I am very meticulous about my vehicles and don't want to change out parts for no reason.
 

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I doubt ALL the injectors are leaking, but you might have ONE or a FEW leaking. A leaking injector can cause NEGATIVE fuel trims, especially at idle or low power demand. When the negative trims exceed -25% (?) it can set rich codes on both banks.

The mechanism as I've learned is when drips of fuel from a bad port injector fall on the hot lower intake plenum, where it turns to vapor, which then gets mixed in the air plenum, where cylinders nearby and possibly ALL are sucking in *unplanned* air + fuel vapor, which the A/F and 02 sensors pick up as 02 deficient, and the PCM reacts by commanding negative trim to maintain closed loop control. The excess fuel vapor is most problematic near idle or low power demand, as plenum air volume and *commanded* fuel is lowest.

The leaking injector issue seems more common for engines with cylinder management, like the Pilot VCM, as the fuel at a leaking injector located at a disabled cylinder leaves deposits as it vaporizes. Versus being exercised regularly for working cylinders, which tends to continuously clean and cool the injector passages and tip.

I am looking into a unusually rich condition on BOTH banks of my '12--both banks have total idle fuel trims of -12% or more, but closer to -2% total trim when cruising and on a slight incline. I suspect a leaking injector or MAF calibration. I'll start by looking at the 4 cylinders that VCM managed, for the 50,000 miles before I had VCM Muzzler installed.
 

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Discussion Starter #3
Would the Check engine light stay on tho if I had a leaky injectors? I guess depends on how bad it's leaking and how rich it is running.
 

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Yes. The leaky injectors (if that's the problem) will continue to cause the codes to set and dash light to stay on. The problem is likely to get worse, where it will eventually effect drivability, fuel mileage, and even possibly damage catalytic converters. That it's bad enough to set both bank codes would warrant repair sooner than later.

My '12 has abnormal fuel trims, but not near severe enough to set trouble codes.
 

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Yes. The leaky injectors (if that's the problem) will continue to cause the codes to set and dash light to stay on. The problem is likely to get worse, where it will eventually effect drivability, fuel mileage, and even possibly damage catalytic converters. That it's bad enough to set both bank codes would warrant repair sooner than later.

My '12 has abnormal fuel trims, but not near severe enough to set trouble codes.
Where are you getting baseline fuel trim #s? Service manual?
 

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Where are you getting baseline fuel trim #s? Service manual?
Base line is Short Term (ST) + Long Term (LT) trim = 0%.

In practice if ST+LT is +/- 5% it is considered nominal by most manufacturers.

Many manufacturer PCM's set codes if ST + LT exceeds 25% or so for longer than a few seconds during a drive cycle. I haven't looked at the Pilot service manual for exact metrics.

If you have a $20 Bluetooth scan tool and the Torque phone app, you can observe ST and LT trims on both banks.
 

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I got my hands on a scan tool, which i was able to get SHRTFT1 & 2, LONGFT1 & 2, and SHRTFTB1S2 & B2S2 ( what ever this is?). If +/- 5 is normal mine are pretty low. See results below all at idle. Looks like Bank 2 is an issue with Bank 1 not being great either.



AVC any input here would be appreciated as I am not familiar with what these #'s are telling me. thx




 

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Your posted short+long trims (engine completely warmed up) are not severe enough to set code/check engine light. Similar idle trims to my '12.

At some point your trims must be going WAY negative and set P0172/0175. Once the codes are set you can retrieve the Freeze Frame data for those codes. In other words, the PCM captures various data PIDS that contributed to setting the code/check engine light.

I did notice on a recent trip that my combined trims approached -25% on both banks right after a fill-up, which makes me believe there is an emissions EVAP issue, allowing raw fuel into the evap canister, which would make the canister vapor very fuel-dense, driving the mixture very rich when the canister is being purged. Even then, the PCM does not set codes. This issue may be entirely unrelated to the chronically negative trims.

I my case, after 30 miles or so, the trims return to -12 to -14% at idle and -2 to -5% while cruising. Still higher than normal, in my opinion. I still haven't had time to further troubleshoot. I do know blocking the canister purge hose doesn't return the trims to "normal".

If one were suspecting a leaking injector, I might suggest a full can of Berryman B-12 into say 1/4 tank of gas and burning that until near empty. Might somewhat or vastly change the trims after the next normal fill up. It didn't change my symptoms one bit, which is why I didn't pursue the leaking injector trail.
 

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The short + long trims #'s I posted are at idle with engine cold. Given they are idle trims with engine cold do these seem low to you?

The dealer cleared my codes so not sure if the Freeze Frame data from when the codes were set would still be there or if they got cleared as well but I can check with my scan tool. I assume they get cleared.

I never heard of Berryman B-12, I will have to research it.
 

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Your posted cold idle fuel trims are not negative enough to have caused the rich P-codes and check engine light. The base line for fuel trims is typically taken on an engine fully warmed up (i.e. 167F to 180F).

As for any clues reagrding what conditions the the rich P-codes were set, they are gone, thanks to your mechanic. Rich codes can be caused by leaking injectors, high fuel pressure, messed up EGR flow to one or more cylinders, MAF or BAP sensor calibration, intake air temp sensor, coolant temp sensor.....freeze frame data can provide a snapshot of many of those, at the moment the code got set. Otherwise, it's tedious evaluation of all those things individually.

B-12 is sold at most Walmarts, Autozones, etc.
 

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Your posted cold idle fuel trims are not negative enough to have caused the rich P-codes and check engine light. The base line for fuel trims is typically taken on an engine fully warmed up (i.e. 167F to 180F).

As for any clues reagrding what conditions the the rich P-codes were set, they are gone, thanks to your mechanic. Rich codes can be caused by leaking injectors, high fuel pressure, messed up EGR flow to one or more cylinders, MAF or BAP sensor calibration, intake air temp sensor, coolant temp sensor.....freeze frame data can provide a snapshot of many of those, at the moment the code got set. Otherwise, it's tedious evaluation of all those things individually.

B-12 is sold at most Walmarts, Autozones, etc.

Thanks AVC, sorry I just saw your reply.

For now no check engine light so I will just keep an eye on it and check the fuel trims with engine warmed up when I get a chance.

On a side note i just realized I have 2 usernames for this site.
 

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So after the education lesson on fuel trim IT kinda did not show if there was any resolution to this? Did this get fixed and what was the final outcome ?
 
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