New to me 06 lx470, 283K on the dash, p0441 and p0455 have been intermittently appearing since purchase. I would bet that this was happening before purchase because the only thing new under the hood is the purge VSV, which is some aftermarket unbranded part.
First thing I did was replace the gas cap with OEM (either from partsouq or lexuspartsnow, i dont remember off the top of my head). The codes stayed away for a half dozen trips or so, but are coming back now routinely.
Second thing was to replace the hose going from VSV to TB (pretty rotten looking). No improvement. The other hose (VSV to hard line running back to charcoal canister) looks fine.
Next I looked more closely at the purge VSV. Purge VSV - 27 ohm resistance between terminal 1 and 2 (within fsm spec), operating as expected with techstream utility (no flow while off, suction while on and engine running, air not able to be forced backward through valve).
So at this point, I think that everythhing in the engine compartment is working as it should.
Next I disconnected the hose running from VSV to hard line and pressurized with air. To my surprise, the air came out somewhere in the area of the fill neck. Thinking that I got a bad cap, I cleaned both mating surfaces again and had the same response.
Finally, i ran the EVAP montitor test through techstream. Here are my results.
I should note that while running the EVAP system test I was almost certain that I could air coming from around the canister pump module. However, I could not demonstrate a gross leak of pressure or vaccum with smoke or soapy water from that location.
So I'm a bit stumped here. I have been over the FSM a dozen times and I still am having a hard time wrapping my head around the EVAP monitor results.
First - If the purge VSV is ON (open), why is the system expecting a positive number and not a negative one? Opening the valve exposes the system to vacum, thus prodcuing a negative number, which mine is doing. But the reference values for that field are positive?
Second - is it normal for the gas cap to vent air when the system is placed under pressure like this? I used my shop compressor and an air gun to do it, so I'm sure there was far more pressure than the system ever normally sees.
Third - the air that I think I can hear moving around the canister pump module - this is abnormal, correct? From what I can tell, this should be a completely sealed system. Although it does make sense that if a pump is moving air, that air has to go somewhere. So is it that the pump creates a vacuum by pulling from the system and expelling to the atmosphere?
At this point the only thing I can think to do is to replace the canister assembly. I hate throwing parts at stuff though without having a formal diagnosis first.
What does everyone think?
Sorry for the long post, this issue has me really fired up. I can tell this has been worked on before (witness marks on the canister and the very small hose coming off of it) and clearly it was never fixed, and the damn dealership who did the PPI clearly never hooked techstream up to the rig or else this would have been caught. The only reason it never came to my attention is because the system doesnt throw the DTCs unless they persist for 2 cycles. Meaning that whoever sold it to me put on the new VSV, cleared the codes, and washed their hands of it.
First thing I did was replace the gas cap with OEM (either from partsouq or lexuspartsnow, i dont remember off the top of my head). The codes stayed away for a half dozen trips or so, but are coming back now routinely.
Second thing was to replace the hose going from VSV to TB (pretty rotten looking). No improvement. The other hose (VSV to hard line running back to charcoal canister) looks fine.
Next I looked more closely at the purge VSV. Purge VSV - 27 ohm resistance between terminal 1 and 2 (within fsm spec), operating as expected with techstream utility (no flow while off, suction while on and engine running, air not able to be forced backward through valve).
So at this point, I think that everythhing in the engine compartment is working as it should.
Next I disconnected the hose running from VSV to hard line and pressurized with air. To my surprise, the air came out somewhere in the area of the fill neck. Thinking that I got a bad cap, I cleaned both mating surfaces again and had the same response.
Finally, i ran the EVAP montitor test through techstream. Here are my results.
I should note that while running the EVAP system test I was almost certain that I could air coming from around the canister pump module. However, I could not demonstrate a gross leak of pressure or vaccum with smoke or soapy water from that location.
So I'm a bit stumped here. I have been over the FSM a dozen times and I still am having a hard time wrapping my head around the EVAP monitor results.
First - If the purge VSV is ON (open), why is the system expecting a positive number and not a negative one? Opening the valve exposes the system to vacum, thus prodcuing a negative number, which mine is doing. But the reference values for that field are positive?
Second - is it normal for the gas cap to vent air when the system is placed under pressure like this? I used my shop compressor and an air gun to do it, so I'm sure there was far more pressure than the system ever normally sees.
Third - the air that I think I can hear moving around the canister pump module - this is abnormal, correct? From what I can tell, this should be a completely sealed system. Although it does make sense that if a pump is moving air, that air has to go somewhere. So is it that the pump creates a vacuum by pulling from the system and expelling to the atmosphere?
At this point the only thing I can think to do is to replace the canister assembly. I hate throwing parts at stuff though without having a formal diagnosis first.
What does everyone think?
Sorry for the long post, this issue has me really fired up. I can tell this has been worked on before (witness marks on the canister and the very small hose coming off of it) and clearly it was never fixed, and the damn dealership who did the PPI clearly never hooked techstream up to the rig or else this would have been caught. The only reason it never came to my attention is because the system doesnt throw the DTCs unless they persist for 2 cycles. Meaning that whoever sold it to me put on the new VSV, cleared the codes, and washed their hands of it.
