Recently have been getting CEL code P0456 - small evap leak.
As the evap system self test is performed at night by the vehicle, usual symptom would be a nice greeting in the morning with flashing CEL, 4LO, TRAC, etc. And the inability to toggle 4LO, CDL, etc., if off-road camping. It progressed over a couple years from rare blue moon nuisance, to continuous every other day. Got really good at using a BT OBD-II dongle to reset in 30 seconds. Interestingly, after many many resets (maybe 30+?), the car will throw like 8 EVAP CELS, then stop complaining on the dashboard, and just keep the internal code. But in order to do CA smog, it needs to be fixed.
I did a bunch of sleuthing and tests and isolated it to no particular external leak, but an internal failure of the Evap Canister (aka charcoal canister). To be fair, there's many ways a small evap leak can manifest. From a simple gas cap seal either not tightened or worn. Or compromised connection or rubber hose leaking externally. Or leaking purge VSV up at the motor. I wanted to be sure it wasn't any of these before I took the effort to drop the aux tank to get at the charcoal canister.
Today, I confirmed that it was indeed the vent VSV integrated in the charcoal canister:
The Leak Detection Pump Sub Assembly is mounted to the charcoal canister assembly by 3x 10mm hex bolts. This sub assembly includes the problem Vent VSV, which is clearly corroded. Before tearing it apart, I tried to jump it, and it was moderately clicking, but did not seal the vent.
The new charcoal canister fixing the issue also confirmed this as the problem.
Plausible that fuel overfilled the evap canister at one point. I'm not as sure of this, because I'm a conscientious owner and don't tend to fill my tanks like that. These components are also made to handle fuel and fuel vapor so they should be designed not to corrode with fuel.
So water/moisture?
Whenever I've experienced issues, first thing that comes to mind is modifications. OEMs spend millions of dollars for environmental, field, and durability tests, especially our vaunted LC. I have an LRA aux tank. There's various plausible reasons but the thing that I suspect is the external breather that is modified with small exposed mushroom filter on the end of a high mounted hose.
Could water be entering from that?
As the evap system self test is performed at night by the vehicle, usual symptom would be a nice greeting in the morning with flashing CEL, 4LO, TRAC, etc. And the inability to toggle 4LO, CDL, etc., if off-road camping. It progressed over a couple years from rare blue moon nuisance, to continuous every other day. Got really good at using a BT OBD-II dongle to reset in 30 seconds. Interestingly, after many many resets (maybe 30+?), the car will throw like 8 EVAP CELS, then stop complaining on the dashboard, and just keep the internal code. But in order to do CA smog, it needs to be fixed.
I did a bunch of sleuthing and tests and isolated it to no particular external leak, but an internal failure of the Evap Canister (aka charcoal canister). To be fair, there's many ways a small evap leak can manifest. From a simple gas cap seal either not tightened or worn. Or compromised connection or rubber hose leaking externally. Or leaking purge VSV up at the motor. I wanted to be sure it wasn't any of these before I took the effort to drop the aux tank to get at the charcoal canister.
Today, I confirmed that it was indeed the vent VSV integrated in the charcoal canister:
The Leak Detection Pump Sub Assembly is mounted to the charcoal canister assembly by 3x 10mm hex bolts. This sub assembly includes the problem Vent VSV, which is clearly corroded. Before tearing it apart, I tried to jump it, and it was moderately clicking, but did not seal the vent.
The new charcoal canister fixing the issue also confirmed this as the problem.
Big question for me is why did this occur? What is the real root issue?
Plausible that fuel overfilled the evap canister at one point. I'm not as sure of this, because I'm a conscientious owner and don't tend to fill my tanks like that. These components are also made to handle fuel and fuel vapor so they should be designed not to corrode with fuel.
So water/moisture?
Whenever I've experienced issues, first thing that comes to mind is modifications. OEMs spend millions of dollars for environmental, field, and durability tests, especially our vaunted LC. I have an LRA aux tank. There's various plausible reasons but the thing that I suspect is the external breather that is modified with small exposed mushroom filter on the end of a high mounted hose.
Could water be entering from that?
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