[marks123.ms]

2018 Pilot with 33K miles showed a CEL and displayed an emission and AWD system problem on the dash. Dealer found P0170 and P0174 and replaced the fuel pump. After reset and a short test drive, the same errors popped up on dash. After the fuel pump swap dealer says there are no error codes showing now and recommended to just drive it (and hope?) that the lights extinguish. Well after driving about 8 or so times, including a 1.5 hour trip, the same error lights are still there. I checked the air intake and around the air filter area and don't see any cracks. I unhooked the battery and the CEL went out only to come back up again after a day. I asked if it could be the MAF or O2 sensor but the dealer didn't that that was the issue. They are suggesting to do a 'valve clearance check' which I'm not familiar with. It seems to drive fine but I can't tell if there has been a decrease in gas mileage yet.

Any suggestions?

 

[ac13]

Did you pull the codes? if light comes on, there got to be a trouble code and you should either calling Honda of North America (if the dealer can't do anything about it and just tell you to drive) or go to a different dealer.

 

[marks123.ms]

The original codes were P0170 and P0174. After inspection of everything else, these codes led the dealer to conclude there was an issue with the fuel pump. Now there are no codes showing but the check engine light and emissions/AWD warning displays on the dash.

 

[ac13]

The original codes were P0170 and P0174. After inspection of everything else, these codes led the dealer to conclude there was an issue with the fuel pump. Now there are no codes showing but the check engine light and emissions/AWD warning displays on the dash.

Did you scan it yourself or you are talking their words for it? if there is no code showing then there should be no CEL. If you don;t have scanner, goto autozone or advance and they will scan it for you free of charge.

 

[marks123.ms]

Did you scan it yourself or you are talking their words for it? if there is no code showing then there should be no CEL. If you don;t have scanner, goto autozone or advance and they will scan it for you free of charge.

I scanned it myself and got P0171 (system too lean bank 1) and P0174 (system too lean bank 2). The dash shows emissions system and AWD system problem light. I contacted Honda of North America and they just replied that they "were unable to find any open campaigns pertaining to this matter (e.g., safety recall, warranty extension or product update)." We bought the car in the US but moved overseas, and the country we are in only has a few Honda service centers so our choices are limited. I tried taking it to a general non-Honda shop but they are reluctant to work on it because it is a more complicated issue that they believe should be handled by Honda.

I could be paranoid, but it now sometimes seems there is a slight hesitation when the vehicle shifts from 2nd to 3rd gear when accelerating. We normally drive it in 'eco mode' but that gets disabled when the CEL comes on.

I cleaned the MAF and checked for any air leaks but that didn't seem to make a difference. The service center thinks that we now need a valve clearance check after they replaced the fuel pump. I did mention the MAF sensor, oxygen sensor, and fuel injectors as other potential causes but they seem to think the valve clearance check is needed. I am losing faith after they originally assured me the fuel pump was the issue.

Thanks in advance for any suggestions.

 

[Cbayman]

While a problem with fuel delivery can cause a lean condition, it will also cause drivability issues as the engine will stumble and have loss of power during acceleration or high speed cruise when fuel flow is high. I’m also pretty sure the PCM would report a fuel pressure DTC if there was a fuel delivery problem. There are 2 fuel pumps on the Pilot; low pressure pump in the gas tank driven by an electric motor and the high pressure pump located under the upper intake manifold driven mechanically. Do you know which fuel pump was replaced? I highly doubt, at 33K, your vehicle needs a valve adjustment and even if the valves clearances were out of spec it most likely would cause mis-fires, not a lean condition.
The fact they told you to just drive awhile to see if the light goes out tells me either the shop is totally incompetent or they’re just ripping you off. A competent tech will always reset the DTC, set the ready codes and verify the DTC is fixed before returning the vehicle to the customer.
You’re on the right track looking for an air leak downstream from the MAF sensor. Since both banks are lean, it has to be a leak common to both banks. Both banks lean also says it’s probably not a bad A/F ratio sensor since it would be highly unusual for 1 sensor to fail at 33K much less likely for 2 failures. A lean condition is easily detected by monitoring the fuel trims using a scan tool. The trims should ideally be 0+/- 5% for both banks. Using your scan tool, monitor the long term and short term for both banks at idle. (These should be available in live data and maybe abbreviated as LTFTB1,B2 and , STFTB1, B2.) For a lean condition failure the trims should be should be at >+20%. This means the PCM has increased the mixture to the max limit but still cannot get to a stoichiometric (ideal) mixture.
Double check the air inlet hose connection to the throttle body to verify the clamp is tight. Check for a leak in the vacuum hose between the intake and power brake booster. Also pull the engine cover and verify no leaks in the PCV hose attached to the top of the intake manifold. And look for a leak between the throttle body and intake manifold.
One trick is to use brake cleaner and lightly spray the joint while monitoring STFT. If you see the trim suddenly go from a high + value towards 0 then you found the leak.
It’s also possible that the MAF sensor is bad or intermittent. The S2000 had an issue where the MAF sensor connector would work loose causing faults. The solution was to zip tie the connector. So check for a loose connector or corrosion in the connector of the MAF sensor.
If you have had the fuel injectors replaced it’s highly likely that repair led to this condition as all of these components are removed to replace the injectors.

 

[AVC]

Valve adjustment would be the LAST thing I'd suspect for a Pilot with 33k miles. Not impossible, if there were manufacturing defects, but I'd rule everything else out first. I'd also rule out all the before and after cat 02 sensors as defective, as both banks started throwing leans codes about the same time, and unlikely to have defective sensors in both banks--the PCM would likely set different codes for that anyway.

Probably not emissions related, as the PCM tests that in nuanced ways for defects/leaks. At least not something I'd chase unless I had related codes.

This needs to by systematically diagnosed; the lean P codes will create freeze frame data, where a good tech will have clues as to conditions both banks where at when they went out of fuel control (generally beyond +/- 25% short+long term fuel trim).

Depending on what they saw in the freeze frame, they might do a Wide Open Throttle run to see if both banks went deeply lean, and if the commanded and actual high pressure fuel rail tracked together. If no, it would merit further investigation of BOTH low and high pressure fuel pumps until the command and actual pressure tracked at various loads.

Otherwise, both banks setting lean codes could be a significant vacuum leak, a ducting leak after the MAF sensor caused by PCV or duct defect, calibration drift with the MAF or MAP, dirty MAF, EGR defect. Many EGR defects are caught by the PCM as excessive flow, commanded vs actual opening errors, etc.

A vacuum leak will often show up in freeze frame data as lean codes at idle or low throttle openings. Lean codes during cruising can be a PCV, EGR or fuel starvation, Lean codes set under heavy load almost always fuel starvation.

I wouldn't initially suspect injector failures, as both banks reported lean codes about same time, and you aren't getting misfire codes, right?

Not an exhaustive diagnosis flow, but a good start.

And I'd get after the dealer/tech who replaced parts that didn't fix it. You're paying for guesses.

 

[marks123.ms]

Thank you for all the suggestions.

In response to questions you all posted:

1. The dealer replaced part # 17045TZ5A10 for the fuel pump. When I picked it up, they told me replacing the fuel pump cleared the codes. They said they took it for a test drive and said they got no more errors. I drove for probably no more than a few miles and the CEL came back on. So I drove it back and they said they checked it and suggested a valve adjustment.

2. The injectors have not been not replaced. This is the first time I have taken the vehicle to the dealer for anything major. Only routine maintenance up to this point.

3. I am not getting any other misfire codes. Only thing that the dealer wrote down initially was P0171 and P0174. Then I checked it yesterday and got the same codes.

4. The scanner tool I borrowed does have live stream data capability. I am a total beginner at most things dealing with vehicles, including using the scan tool, so there might be some user error here....

Without the engine running:
short term trim bank 1: 0%
long term trim bank 1: 33.6%
short term trim bank 2: 0%
long term trim bank 2: 33.6%

At idle:
short term bank 2: 35.9%
long term bank 2: 33.6%
(sorry i didn't take a picture of the display for bank 1 output at idle)

I took pictures of all the data screens and attached them to this post.
.
I am not sure if any of that helps, but I can borrow the tool again and capture any other data that might help figure this out. Is it best to capture the data while at idle and on the move?

Really appreciate the suggestions as we are outside the US and also dealing with a slight language barrier when it comes to more advanced car/mechanical- related vocabulary!

 

[Cbayman]

That is the part number for the low pressure fuel pump in the fuel tank. The data is pointing to a vacuum leak. Inspect for a missing or broken vacuum hose or crack in the air inlet hose. This really should not be a difficult diagnosis for a technician. I would not go back to that same shop as they seem to be guessing at your expense. Pull the engine cover and do a thorough inspection. I bet you’ll find the problem.

 

[WayneM.]

A technician worth half his salt could do something with the data you’re showing here.
You mentioned that you’re overseas? Can you elaborate on this, and give some info about the fuel you are using?

 

[marks123.ms]

Great, thanks for the pointer on the vacuum leak. I did a thorough inspection of the air intake after the air filter box and didn't see any cracks. Any good tutorials on how I can check the vacuum leak at home? I am going to take it to a local shop who deals with non-South Korean cars this week.

We are in South Korea but we use normal 87/89 octane gas.

 

[WayneM.]

We are in South Korea but we use normal 87/89 octane gas.

What is the ethanol content of the fuel that’s currently in your tank? Go back to that station to check this, if you must.

 

[Cbayman]

I’m assuming the only symptom you’re getting is the CEL with P0171/P0174. If you had a fuel delivery issue the vehicle would run poorly while accelerating or high speed cruising. A vacuum leak will have greater impact at idle because the engine is using the least amount of air at idle and therefore the leak will have a greater effect. Since you’re not getting misfires, the leak probably isn’t real large. So you’re looking for a cracked vacuum hose, loose clamp, etc. The engine cover simply pulls off. Once removed you will see the black plastic upper intake. There you will see the PCV hose on top, the brake booster hose on the back and there is a purge valve hose on the rear driver side which is hard to see. Basically inspect these hoses for cracks or rodent damage. There also a hose connected to the intake air tube that is the fresh air input for the PCV system. Need to follow that to the rear valve cover and make sure it’s connected.

 

[WayneM.]

You can easily find a vacuum leak with the engine running and both bank short trim data. Just obtain a can of carburetor cleaner and spray around the engine/ intake area and watch for the short trim to move back towards zero.

 

[marks123.ms]

What is the ethanol content of the fuel that’s currently in your tank? Go back to that station to check this, if you must.

We fill up on a US military base. I believe the gas is shipped in from the Gulf Coast region. So I assume it is similar or same to what you get in the US.

 

[marks123.ms]

Here are a couple of videos if it helps with any kind of suggestions:

This one is just a shot under the hood. I did zoom in on the air intake near the MAF because it looked like a crack, but I confirmed there is no crack and it was just dust.

New video by Mark S

photos.app.goo.gl

This one is starting up stepping on the accelerator in park. I do notice a difference in sound when stepping on the accelerator.

https://photos.app.goo.gl/RSeWLkSV65t3Bm1k7

Thanks again for the collective wisdom.

I’m assuming the only symptom you’re getting is the CEL with P0171/P0174. If you had a fuel delivery issue the vehicle would run poorly while accelerating or high speed cruising. A vacuum leak will have greater impact at idle because the engine is using the least amount of air at idle and therefore the leak will have a greater effect. Since you’re not getting misfires, the leak probably isn’t real large. So you’re looking for a cracked vacuum hose, loose clamp, etc. The engine cover simply pulls off. Once removed you will see the black plastic upper intake. There you will see the PCV hose on top, the brake booster hose on the back and there is a purge valve hose on the rear driver side which is hard to see. Basically inspect these hoses for cracks or rodent damage. There also a hose connected to the intake air tube that is the fresh air input for the PCV system. Need to follow that to the rear valve cover and make sure it’s connected.

The only other symptom i seem to notice is possibly some hesitation when shifting from 2nd to 3rd gear. I don't notice any other major issues when driving but I haven't been driving it at high speeds until this issue is resolved.

 

[WayneM.]

Mark, what I’m concerned about is the ethanol content in your gasoline. If it’s ethanol heavy, it will cause your problem.

 

[AVC]

A couple of observations about the data and video you posted;

The engine sounds mechanically OK; stable idle, no visible vibration. Assume for now good compression, no valve issues, no timing belt issues.

You are missing the first screen shot of the scan tool while idling; missing Bank 1 short and long term, as %.

Missing MAF readings for engine off and idle.

High pressure fuel rail pressure seems reasonable, although I haven't measured normal for Honda direct injected V6. No high pressure codes, so assume it's within reasonable tolerance of commanded pressure (not shown in your data).

Bank 2 is in control, but adding a whopping 70% fuel trim at idle to get there

With +70% fuel trim, pretty sure you'd hear that large of a vacuum leak, if that were the cause, in the video.

Would be helpful to have some steady cruising and Wide Open Throttle MAF, MAP, Fuel trims both banks, rail fuel pressure.

Without other data, I'd be guessing. So if I WERE guessing, I'd first eliminate whether the MAF is whacked for calibration--inspect very carefully for debris, fuzz on the sense wires. And/or swap MAF's with another direct injected Pilot or Ody.

 

[WayneM.]

2018 Pilot with 33K miles showed a CEL and displayed an emission and AWD system problem on the dash. Dealer found P0170 and P0174 and replaced the fuel pump. After reset and a short test drive, the same errors popped up on dash. After the fuel pump swap dealer says there are no error codes showing now and recommended to just drive it (and hope?) that the lights extinguish. Well after driving about 8 or so times, including a 1.5 hour trip, the same error lights are still there. I checked the air intake and around the air filter area and don't see any cracks. I unhooked the battery and the CEL went out only to come back up again after a day. I asked if it could be the MAF or O2 sensor but the dealer didn't that that was the issue. They are suggesting to do a 'valve clearance check' which I'm not familiar with. It seems to drive fine but I can't tell if there has been a decrease in gas mileage yet.

Any suggestions?

Do you have any more background info on this issue? Now that we know you’re in a different country with the vehicle, did this happen before the move? I’m still thinking that something happened or changed recently to cause this.
The other thing I think you should do is get to a professional scan tool to see if there are any other Honda specific DTCs.

 

[Cbayman]

How long have you been in country? And when did this first start occurring with relation to when the car arrived in country?

Some other ideas:

• It would be unusual at 30K miles but maybe the PCV valve is stuck open. This valve is supposed to be closed at idle. While monitoring the fuel trims with a scanner, try pinching off the PCV hose, it’s the hose on top of the intake plenum. If the STFT fuel trims moves from >+20% towards 0 then inspect all the hoses associated with the PCV system. If no anomalies are found, replace the PCV valve.
• Again, it would be unusual but maybe the brake booster is leaking. Test for this by pinching the hose going to the brake booster and observe any impact on fuel trims.
• The EVAP purge valve is located behind the throttle body. It will have an electrical connector, a hose connected to a line on the firewall ( this is the purge line going to the fuel tank area) and a vacuum line connected to the intake manifold. This valve could be faulty or cracked. Pinch the vacuum line and look for a change.