How long can you keep just keep clearing P0456 code (Evap leak) (1 Viewer)

[kcjaz]

I started getting this code a few months back and have just been clearing it and essentially ignoring it. I did replace my gas cap but that didn’t seem to have any affect. I also don’t daily drive it. I am daily drive it this week and it’s seems I’m now getting the code every 2 or 3 days. I think this is because it does a system test of some kind every couple days and when it fails on the retry, it throws the code.

I am planning on going to cruise Moab next week. I’m also planning on just resetting the code every two days as necessary to get through the week. There’s no way I’m dropping the gas tank and messing with that system to try to fix whatever is wrong before cruise Moab

Ultimately, how long can you keep just ignoring this? One lucky thing about living in Kansas is that I do not have any emissions test to deal with.

 

[kcjaz]

Bump

 

[Romer]

I would think indefinitly unless it turns into a bigger problem

As long as you have your reader with you, you can reset it and the 2-3 days is the non keyed test.

What it prevents is switching in and out of 4WD Lo. It doesn't hurt anything else while you are driving. Say it happens on the highway, just keep driving until you get Moab and are ready to switch to 4WD LO.

Say it happens on the trail, no need to worry about it until you need to go back to 4WDHI

 

[kcjaz]

I would think indefinitly unless it turns into a bigger problem

As long as you have your reader with you, you can reset it and the 2-3 days is the non keyed test.

What it prevents is switching in and out of 4WD Lo. It doesn't hurt anything else while you are driving. Say it happens on the highway, just keep driving until you get Moab and are ready to switch to 4WD LO.

Say it happens on the trail, no need to worry about it until you need to go back to 4WDHI

Thanks.

One thing about my Tesla screen set up that I love is that I run OBDFusion to monitor a bunch of stuff like tranny temps so it’s easy to read codes on the fly (not while actually driving of course) and clear them. I don’t have to get out a reader, I have one that’s always connected.

It always happens right after I’ve started the truck and it’s takes 2 minutes to clear. I’ve never had the blinking “Lo” light appear while driving. I think there are other related evap codes that do the same thing so maybe those can hit while driving.

 

[Romer]

even better

P0456 is a small leak detection. Could be knick in hose or loose clamp. Did you take the inner fender cover off to inspect that area? Maybe the vent filter came off and the hose then became plugged.

I know you have been through the various threads

 

[kcjaz]

even better

P0456 is a small leak detection. Could be knick in hose or loose clamp. Did you take the inner fender cover off to inspect that area? Maybe the vent filter came off and the hose then became plugged.

I know you have been through the various threads

Yes, I looked at that when I replaced the gas cap. I’ll do more troubleshooting after CM. You going to CM? Hope to see you there!

 

[Romer]

Yes, I looked at that when I replaced the gas cap. I’ll do more troubleshooting after CM. You going to CM? Hope to see you there!

Not this year. It will be the 3rd CM Imissed in 20 years

 

[kcjaz]

So the morning I was leaving for Cruise Moab, I filled the tanks and noticed I was leaking fuel. I took the fender liner off and inspected the pump, charcoal filter and hoses. The hose clamp on the fuel fill line was loose and the source of the leak. I assumed it was also the source of the evap codes.

The second day of Kokopelli, she through a different evap code. I don’t recall the number but it was a failed purge test. I cleared it and went on. The next day it happened again but my OBD2 app wouldn’t run so I could’t clear the code. Luckily, a guy in the group had a code reader. It was a high end Snap-On code reader and it discovered a whole lot of codes my OBD Fusion app didn’t report. We cleared the evap code and all of the other engine codes. I haven’t had it throw another evap system code since so just about a week and a half.

I recently bought a Launch code reader but haven’t used it yet. I need to play with it. I guess I was pretty ignorant thinking all code readers would identify all codes. It seems that the Snap-on found something that the OBD Fusion app didn’t.

 

[Artie]

So the morning I was leaving for Cruise Moab, I filled the tanks and noticed I was leaking fuel. I took the fender liner off and inspected the pump, charcoal filter and hoses. The hose clamp on the fuel fill line was loose and the source of the leak. I assumed it was also the source of the evap codes.

The second day of Kokopelli, she through a different evap code. I don’t recall the number but it was a failed purge test. I cleared it and went on. The next day it happened again but my OBD2 app wouldn’t run so I could’t clear the code. Luckily, a guy in the group had a code reader. It was a high end Snap-On code reader and it discovered a whole lot of codes my OBD Fusion app didn’t report. We cleared the evap code and all of the other engine codes. I haven’t had it throw another evap system code since so just about a week and a half.

I recently bought a Launch code reader but haven’t used it yet. I need to play with it. I guess I was pretty ignorant thinking all code readers would identify all codes. It seems that the Snap-on found something that the OBD Fusion app didn’t.

I had assumed that OBD Fusion read them all… good info. I have that launch thing as well but it’s as user friendly as a porcupine.

 

[JeffsLC]

I have a separate but related question.

I had a 12.5 gal long range tank on my ‘21 LC200H for a couple years with no issues. This spring I threw a code (don’t know which) and the cruise control would not work. I paid $$$ to have the tank dropped and the charcoal filter replaced/repaired (obviously I lack sufficient tech skills/experience to fully understand - or fix - the problem). I drove a couple thousand miles with no problem, and then threw the code again. I was told topping off my tank(s) often caused the issue (which I’d been doing forever) but stopped now. To avoid repeated issues, I had the LR tank removed (more $$$) and have not had a problem since. Given that I had no problem for a couple years, I have to believe there is a problem here that can be fixed. I really enjoy the extra reach with the LR tank and would like to have it re-installed but am searching for answers/remedies/etc before doing so.

Has anyone experienced this issue and was it fixable?

 

[kcjaz]

I have a separate but related question.

I had a 12.5 gal long range tank on my ‘21 LC200H for a couple years with no issues. This spring I threw a code (don’t know which) and the cruise control would not work. I paid $$$ to have the tank dropped and the charcoal filter replaced/repaired (obviously I lack sufficient tech skills/experience to fully understand - or fix - the problem). I drove a couple thousand miles with no problem, and then threw the code again. I was told topping off my tank(s) often caused the issue (which I’d been doing forever) but stopped now. To avoid repeated issues, I had the LR tank removed (more $$$) and have not had a problem since. Given that I had no problem for a couple years, I have to believe there is a problem here that can be fixed. I really enjoy the extra reach with the LR tank and would like to have it re-installed but am searching for answers/remedies/etc before doing so.

Has anyone experienced this issue and was it fixable?

There are several threads on this general topic of AP system issues associated with LRA tanks. My take is this:

When adding an LRA tank you also add multiple connections that are new opportunities for system leaks. You are also adding an additional volume associated with the new tank for which the OEM evap system wasn’t sized for. I’m not sure what the impact really is but it could affect the system’s ability to purge the fuel vapor causing the system to see abnormal pressures which could cause codes to be thrown. It could also degrade the charcoal filleted faster.

IMO, most issues are likely leaks. Many here have taken the time to troubleshoot and find there leaks. Doing so can be a bit difficult if you end up dropping the tank to get access to connections or the evaporation canister. If you can’t do this DIY, paying someone could be expensive and time consuming.

I believe I found my leak. I got lucky and it was on the filler neck. After I had all my engine codes cleared at Moab, I have had any more codes thrown (big knock on wood here).

I love the added range and there is zero chance I’ll delete the aux tank. I’ll do whatever I have to to figure out any future issues. If I have to drop the tank, so be it. I’ve got a good shop situation and very soon, the luxury of time.

 

[JeffsLC]

Thanks very much.

 

[grinchy]

I’ve been clearing evap codes every two or three days for a year. My root cause is failed power wiring on a canister relocation. Sometime this summer I’ll get to replacing the wire run, probably.

Aside from the 15 seconds it takes to clear the codes, I haven’t seen any other negative symptoms.

 

[TeCKis300]

I have a separate but related question.

I had a 12.5 gal long range tank on my ‘21 LC200H for a couple years with no issues. This spring I threw a code (don’t know which) and the cruise control would not work. I paid $$$ to have the tank dropped and the charcoal filter replaced/repaired (obviously I lack sufficient tech skills/experience to fully understand - or fix - the problem). I drove a couple thousand miles with no problem, and then threw the code again. I was told topping off my tank(s) often caused the issue (which I’d been doing forever) but stopped now. To avoid repeated issues, I had the LR tank removed (more $$$) and have not had a problem since. Given that I had no problem for a couple years, I have to believe there is a problem here that can be fixed. I really enjoy the extra reach with the LR tank and would like to have it re-installed but am searching for answers/remedies/etc before doing so.

Has anyone experienced this issue and was it fixable?

I've had my LRA 12.5G for many years awhile now.

One thing I noticed is that in extreme temperature swings or elevation changes, especially overnight, that it can trip some of the evap tests and cause CELs.

They're usually small leak evap tests failed or some minor variation. This occurs very very seldom in my setup but I've noticed its particularly on trips where there is that dynamic. I've heard of stock vehicles tripping these too and we fondly refer to them as "MOAB Cels"

I do think the extra volume of the LRA (maybe even more so the larger aux tanks) can create the likelihood of test parameters falling out of norm. Not necessarily indicative of a real problem but it's surely an EPA annoyance.

They're easy enough to clear as noted above.

 

[linuxgod]

FYI I’d have to look in the FSM but it usually takes a few days because IIRC the leak test requires 3 failures of the drive cycle, or something like that. Or maybe I’m remembering wrong and confusing it with another test. But I’m pretty sure when you reset the codes you need the system to run a few drive cycles before they can reappear. It’s not harmful to the truck, but if your state has emissions testing you won’t pass.

 

[JeffsLC]

All of the responses are appreciated. My only note is when my truck threw a code, the cruise stopped working. Should clearing the code fixture that, or does the root cause of the code need to be fixed? Does anyone have a recommendation for a tool that will read and clear the codes? Many thanks.

 

[kcjaz]

All of the responses are appreciated. My only note is when my truck threw a code, the cruise stopped working. Should clearing the code fixture that, or does the root cause of the code need to be fixed? Does anyone have a recommendation for a tool that will read and clear the codes? Many thanks.

When an evap related code is triggered, whatever the reason, it causes the truck to disable other, unrelated things like it won’t let you shift in to or out of 4lo and probably cruise control too. This is why you need to be able to clear the codes. You are not hurting anything by clearing the code and driving. At some point, you probably want to find the root cause if possible. Mine was a fuel fill line leak that was also dumping gas on the ground. Certainly no bueno and needed fixed. Depending on where you live, you may also have an annual emissions test to pass and evap code errors might be an issue.

I use the OBDFusion app on my phone and also my Android head unit. You also need an OBDII dongle. There are Bluetooth Wi-Fi and hardwired versions of those. I use a Wi-Fi version. It sets up its own little Wi-Fi network between the truck and the phone. Bluetooth would be just fine also. Or just go get a dedicated code reader lots of those on Amazon.