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Discussion Starter · #1 ·
Hey Guys, looking for some guidance on this one... My CEL has been lit up for the past few months, after changing my gas cap, replacing the PCV valve, air filter, a few hoses and checking the VCV valve I couldn't get the code to clear. Due to the fact my inspection is due at the end of next month I finally brought it to a garage that I used to use and trust. They charged me the typical $80 diag fee which I was OK with, claim they ran the smoke test and low and behold they claimed the evap canister needed replacement. I was hesitant at first as it seems to be the most expensive part to fix, however given the fact my truck has 170k miles on it and my past relationship with these guys I went ahead and gave them the OK.... Lot's of dollar bills later and 200 miles (drive cycle) I'm still throwing EVAP codes, however instead of the P0456, now I'm throwing P0442 and P0441. Prior to bringing it back to them, I was curious if anyone has had the same issue happen to them. I'm hoping they resolve the issue without any additional money out of my pocket due to the fact that it appears I paid $80.00 for wrong diagnosis and another multiple hundred dollars on a part that I may have not needed in the first. I'm trying to keep my frustration out of this as I do not want to come across too stern to the garage, can anyone give me what kind of "resonable" outcomes I can expect?? Thanks Guys!
 

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Mambeau / Admin
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On a 2003 5VZ, the P0456 is basically a variation on a P0442. Both codes refer to a leak condition in the EVAP system, as detected by a pressure rise. A sudden pressure rise (substantial leak) gives a P0442. A small pressure rise (small leak) trips a P0456.

Here (attached) is the 2003 diagnostic section on P0442 / P0456.

As you can see, it 'might be most anything'.

It could be the canister - especially if the canister itself is leaking (cracked, etc.).
 

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Mambeau / Admin
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Are you throwing P0442 *AND* P0441 at the same time? Or just one at a time?

This might be a clue (see the code output table on page DI-363 of the attachment I posted).
 

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Discussion Starter · #4 ·
Throwing both at same time... After the canister replacement... Prior to the canister replacement I was throwing p0456....
 

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Run the engine, go under the hood and spray some raw propane around your intake and hoses.. Listen for the engine to surge if you hit a leaky spot. Same code kept poping up on me and i eventually noticed a broken vac line /)


Sent from my iPhone using AG Free
 

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Mambeau / Admin
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The P0441 diagnostic document is too big to post here as an attachment. You can access it at:

http://www.ncttora.com/fsm/2003/Repair_Manual/03tacoma/di/eg5vzfe/cip0441p.pdf

It gives the same complex and confusing laundry-list of possible causes.

The fact that you're NOT throwing a P0446 makes me suspect that it's not the VSV for CCV or the VSV for pressure switching valve.

This would leave the VSV for EVAP (or some blockage / leakage elsewhere).

It's also important to bear in mind that a malfunctioning (e.g., 'sticky') VSV unit or an electrical issue in the control / sensor circuits might be causing the pressure / EVAP auto-testing to fail.
 

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Discussion Starter · #7 ·
Thanks guys, this has been such a PITA over the past few months, I thought throwing money at a "professional" last week would have finally solved my problems, but so much for that. It's going back to the same shop who charged me for the diagnostic and swore to me it was my evap canister tomorrow. Curious to see what they say and if they are going to try and squeeze anymore coins out my pocket...
 

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Mambeau / Admin
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There's always the possibility that your EVAP system had multiple issues, and the canister really was a reasonable swap-out to have done. It's just that correcting a leakage at the canister aggravated leaks (or whatever ...) elsewhere in the EVAP system.
 

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Discussion Starter · #9 ·
OK guys thanks for all the help, I brought the truck back in last week but they couldn't run a smoke test b/c the tank was full?? Anyway, ran it down to 1/2 tank, brought it back today and they now they are telling me I need a new tank and sending unit due to staining on top of the tank...They claim they were unable to find any leaks with the second smoke test and that the small evap leak must be coming from the tank itself....any thoughts? thanks!
 

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Mambeau / Admin
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It's entirely possible that the detected leak condition is happening back at the tank (and / or the stuff connected to it).

Unfortunately, that's about all I can say ... :shrug:

Is there any corrosion or damage on the tank itself - something to suggest it may be the source of the leakage?

I'd be tempted to ask them to replace the lines / etc. around the tank (but not the tank itself ...) to see if that solved the leakage problem without replacing the tank.

However, if that doesn't fix the problem you'd end up needing to replace the tank anyway, and that would probably mean you'd have to spend considerably more than if you'd gone ahead and replaced everything the first time around.

I just don't know ... :shrug:
 

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Discussion Starter · #11 ·
Thanks Enola, any idea where I can find a write up on the replacement?? Thinking of trying it myself to save some money....if its even worth it.... thanks
 

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Mambeau / Admin
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I don't have any detailed writeup on changing out the fuel tank itself.

Did the shop do all the pressure testing the FSM calls for? I'm attaching the diagnostic procedure to illustrate all the things that one might have tested.

Because there are pressure / vacuum lines running from the tank forward to the engine bay, there's always the possibility there's a leakage somewhere in between.
 

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I would really get in writing what test from the FSM that points to what they want to replace next before you pay them for any more work. What Enola mentioned
 

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Discussion Starter · #14 ·
UPDATE: Just picked up the truck from the dealership. I wasn't happy with the "recomendation" for a new tank and thought the dealership would be my best option for a 2nd opinion. Toyota ran the smoke test and found no leaks, they ran the FSM tests on the valves and all were functioning properly. They advised that the aftermarket gas cap is the culprit, they swapped out the aftermarket cap I put on when the CEL first came on back in May, and they cleared the code. Now I just have to drive it and hope the cap was the problem. When I dropped the truck off this morning I made no mention to the dealership about the shop wanting to replace the tank, I just said the shop couldn't find the problem. The service guy was telling me that they have had to replace a few tanks and that they typically rot from the top down, so that did give the previous shop some credit. Guess if the CEL comes back I"ll probably have no other option but to swap out the tank, my fingers are crossed...
 

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UPDATE: Just picked up the truck from the dealership. I wasn't happy with the "recomendation" for a new tank and thought the dealership would be my best option for a 2nd opinion. Toyota ran the smoke test and found no leaks, they ran the FSM tests on the valves and all were functioning properly. They advised that the aftermarket gas cap is the culprit, they swapped out the aftermarket cap I put on when the CEL first came on back in May, and they cleared the code. Now I just have to drive it and hope the cap was the problem. When I dropped the truck off this morning I made no mention to the dealership about the shop wanting to replace the tank, I just said the shop couldn't find the problem. The service guy was telling me that they have had to replace a few tanks and that they typically rot from the top down, so that did give the previous shop some credit. Guess if the CEL comes back I"ll probably have no other option but to swap out the tank, my fingers are crossed...
I know this is almost a decade later, but did you ever figure out definitively what the issue was? I’ve been having the same issue, almost verbatim, and it’s driving me insane. Replaced the evap cannister, filler neck, a few hoses, gas cap, emissions sensor, and passes smoke test. Nothing has worked.
 
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