Small EVAP leak

[mark]

Hey all,

New to the forum. I have frequented others before this, but I’m looking to branch out to a non-brand specific forum. My question is as follows. I have purchased a 2014 Nissan Frontier S and after two days I have developed a small evap leak. This has not triggered any DTC’s yet but is documented in the mode $6 as exceding parameters (AKA FAILURE) in EVAP Monitor. Now rember I have had this vehicle for two days only. I visually inspected the purge valve because it is easy to access and noticed a petroleum residue below the valve. Can fuel vapor leave such an obvious trail? Say if there was a pinhole leak directly above a hot surface? If anyone would like to chime in, I am curious to learn more.

Thanks
Mum

Attachments:

• image.jpg

Topic

[college man]

Evap leaks such as this can be hard to pin point. The best way is with a smoke machine.
Will the vapor leave a residue for you to find? There is always that chance but slim. Inspect
your gas cap and make sure its tight and an OE cap.

[mark]

Can anyone else second that fuel vapor can or will leave a residue. All the literature I have read states that these leaks are extremely difficult to find. Also, why is this not triggering a p0456 as I believe it should according to the factory service manual stipulations…??

Attachments:

• ScreenShot2016-02-27at9.22.11PM.png
• ScreenShot2016-02-27at9.52.01PM.png

[mark]

bump… anyone familiar with Mode $06 EVAP codes?

[Richard Kirshy]

The chances that a vapor leak will leave a residue is extremely small if at all … its vapor not liquid.
I concur with college man,
A smoke test is most likely the best way to track down the EVAP leak and check you gas cap.
If you found liquid gas residue coming from the purge valve, ….
My guess is that the tank had been over filled to the point where liquid fuel was drawn to the valve.
BTW, I own a Nissan Xterra and randomly get this warning P0456 or P0442 with no CEL.
At this point I’m 98% sure it is due to the O ring seal on the gas cap.

[mark]

Thanks for the response. I’m not sure where the leak is occurring, just pointing out that a residue was found near components associated with the EVAP system. I would imagine the hoses would be the weakest link. Anyway no codes OR warnings are being triggered and I am curious, why not? At this point I am not trying to find the leak but rather understand the ECM programing and the EVAP Drive Cycle.

[Richard Kirshy]

EVAP Drive Cycle

What to Do When the Drive Cycle Won’t Complete

Step One: Double Check Vehicle Preparation

Have the fuel tank between 30 and 70 percent full. Some systems, especially the EVAP system, need to have a specific level of fuel in order for the tests to be trusted. If the fuel tank is near empty or completely full, many of the basic tests will not run at all.

The vehicle must also have a good alternator and a strong battery. If you have to occasionally jump-start your vehicle, all of the memory from the powertrain control module (PCM) is erased, which includes the data that accurately tracks the results from various stages of the Drive Cycle. Also, if the battery is weak or undercharged, some of the most important tests will never run.

The vehicle must sit overnight, or for at least eight hours, in an environment that is less than 90° F. The engine temperature needs to match the air temperature in order to establish an accurate baseline for the testing. If the outside temperature is over 90° F, the fuel is too volatile and the EVAP system won’t even try to run its tests, though some of the other emissions systems may run their tests.

The keys must be out of the ignition and all of the doors must be closed while the vehicle sits over night because many of the onboard computers “boot up” when the keys are in the ignition. Also, many of the onboard computers still run until all of the doors are closed after the vehicle is shut off and the keys are removed.

Step Two: Repeat the Basic Drive Cycle

Follow the Basic Drive Cycle steps faithfully. Make sure to keep the speed on the freeway between 55 and 60 mph for a minimum of five miles. Please use the cruise control to help you maintain speed and stay in the right lane for safety reasons.

Step Three: Take Note of Which Drive Cycle Monitor(s) Did Not Complete

Drive your vehicle to your regular shop and have them re-check your readiness monitors, present codes, and pending codes. They should do this as a courtesy and for free.
If all of your monitors are “ready” and there are no present or pending codes, then your vehicle has been properly repaired and is ready for an emissions inspection and for normal driving.
If your monitors are not “ready,” then take note of them.
If a Check Engine Light illuminated and/or a pending code was set, the repair shop who worked on your vehicle did something wrong. They need to re-do their work, for no additional charge, unless a totally new and unforeseen trouble code has occurred.

Step Four: Prioritize Which Monitor to Address

In most cases, the three continuous monitors will complete. These constantly monitor the sensors, the fuel mixture, and the occurrence of misfires.
If the oxygen sensor heater monitor is not ready, check to see how many other monitors are not ready. If the oxygen sensor and catalyst monitors are also not ready, the culprit is most likely a weak battery. If your battery is more than four years old, replace it and re-run the Drive Cycle. Even though your car may start just fine, the PCM is hypersensitive to the slightest glitch in the battery. It will suspend the Drive Cycle if it is not happy with any aspect of battery performance and/or charging system performance.
If only the oxygen sensor heater monitor is not ready, but the oxygen sensor monitor, catalyst monitor, EVAP monitor, secondary air system (if applicable), and EGR system (if applicable) are ready, then, in almost all cases, the heater monitor will eventually set and be “ready.” When a heater circuit is getting old, it can be one of the last monitors to pass. But if the oxygen sensor and catalyst monitor are ready, then the heater has to be working or the other two monitors would fail and set codes.
If the EVAP monitor is not ready, verify that your fuel cap is tight and the level of fuel is between 1/4 and 3/4 full. If all the other monitors are ready, then do a couple more “cold” starts. If the EVAP monitor still has not passed or set a pending or present code, then take your vehicle to a shop that employs technicians who are familiar with the Mode 6 Diagnosis.
If none of the other monitors set, you should also take your vehicle to a shop that truly understands Mode 6 Diagnosis.

[mark]

Thanks Nightflyr,

I will try to enable a new Drive Cycle as my commute to work (in town) does not qualify and see what happens. And where is this information found? No mention of Drive Cycle in FSM (EC) Engine Control System section.

[Richard Kirshy]

Just need to Google EVAP Drive Cycle.
The basics are pretty much the same for most vehicles.

[Author]

Replies