P0471 TCC Stuck Off (and a bonus P0442)

God, I can't catch a break these last few months.

New code popped. P0471. Torque Converter Clutch Circuit Performance / Stuck Off. AT fluid levels good, doesn't smell burned. No decernable symptoms. Not a lot else on the forums, so I suppose it's not common.

Battling some other issues recently, misfiring, got new injectors, long crank, new air filter, purge valve, cleaned throttle body. Still idles slightly rough. This TCC code wasn't present a month ago when I was figuring out the misfires.

Truck "bumps" when coming to a stop but has done that for years. Other folks here have said it's normal and keep the drive shaft joints greased.

Haven't noticed any issues shifting. Wondering where to start.

I'm not sure if the rough idle is related to the small evap leak (it passed a smoke test years ago) or if it's something new that's been brewing with the TCC

 

It shows three codes, what are the other two?

The clunk at stopping for me was driveline, greasing the u-joints. But that said, P0741:






I can't find P0471 in the FSM, for any of the years I have.

 

Other codes are for the small evap leak. One active, one stored.

Thanks shifty

 

Note the cracked fuel filler neck TSB for 2003-2004 trucks may be related to your case. See here.

 

I was towing a trailer a few days ago, and since my CEL was already on, my theory is that something about that ride made it pop the new code. I had overdrive turned off and it was only an 18 minute drive. Approx 3,500lbs trailer. But I did want to get home and was gunning it.

 

If you're talking about the EVAP code, it shouldn't have mattered.

The following is true for the vast majority of EFI (fuel injected) vehicles, and at least having a basic understanding of it will save you oodles of cash and frustration.

Virtually all EVAP codes have one primary source: The sealed fuel/vacuum delivery and return system. Those codes being P0441, P0442, P0446, P0447, P0456 and so on.

Fundamentally, everything between your gas tank and fuel rail/intake is a controlled sealed system. You have fuel supply/return lines from the tank to the fuel rail(s) and back, and you have vacuum lines at various places in between ... like between the fuel filler neck and tank, the tank and charcoal canister, the charcoal canister and intake/engine.

That whole system I just described needs to maintain a specific level of sealed nature, meaning:

• As you draw fuel into the engine to be burned, vacuum is naturally created in the system as you remove liquid fuel to burn, but replacing it with nothing (except vacuum)
• The ECU can easily monitor how much pressure is building up in the system as you remove spend/remove that fuel
• The vacuum created helps the system reclaim any unburnt fuel vapors, to be re-burned

Obviously, you can't just keep burning fuel constantly, the vacuum pressure would become so great the fuel tank would crumple. To avoid this, most vehicles have one or two places in all those lines with purge/vent valves ("VS Valve" or "VSV") to release the pressure when the ECU sees it's getting too high.

That's the basic of the system. The ECU will throw EVAP codes when it detects something is out of whack, the two big cases being:

• Pressure too high: It thinks a vent/purge valve is stuck closed
• Pressure is too low: It thinks a vent/purge valve is stuck OR it thinks there's a leak, either small or big, like the gas cap's not fully tight, the charcoal canister or one of its vacuum hoses is cracked/loose

So, basically the code you're getting right now is your ECU saying, "Yo dawg, you got a leak somewhere, and I can't hold/control vacuum properly!!"


The following diagram shows a simplified version of your V6's EVAP system, which is very similar to the V8's system (overall). I shifted some things around from the FSM diagram, and deleted some clutter so it's not overwhelming. It does a good job of pointing out where the ECU is looking for leaks, overall, everything in that dashed area needs to remain sealed, or codes will trigger.

• The ECU (or ECM in this pic) has lines to both vent/purge valves, as shown, to control overall pressure, opening the valves if pressure is too high, closing them to raise pressure, all to optimize fuel burn.
• The green 'EVAP service port', I'm sure you've seen that under your hood in the engine bay, where it typically lives, that's where you'd hook up a smoke tester to find leaks in the system.
• I think in the 2003, the charcoal canister is above/beside the gas tank similar to my 2006, it has vacuum hoses on it that can crack or come loose and cause a small or large leak code, but the body itself can also take a hit offroading and get cracked, for example.
• You'll notice three possible places the system can be open to air: At both charcoal filters (highlighted yellow), and at the gas tank's cap; the charcoal filters help capture any vapors that may sneak by.
• The gas cap is actually part of the EVAP system, it has a pressure-sensitive seal on it too, which is why you always need to tighten until it clicks at least 1x-2x, if it's not secured 'til click, the system won't be sealed (P0441 is a common failure or 'cap is loose' code).
• The filler neck TSB exists because, if there's a crack or seal failure between the cap and tank, i.e. at the fuel filler neck, that crack will impede the ability of the ECU to maintain vacuum in the system.

Nutshell: If your valves aren't stuck open (there are specific codes for that), and you have a minor leak, it's probably a vacuum line, gas cap, or plastic line/canister that's cracked; if it's a gross/large leak, you probably have a major hole in the system, detached hose, or similar. I have heard cases where, for example, a small pebble gets stuck in a purge valve or - fun one here that happened a lot with some GM trucks - flying insects will pack the tubes coming off the vent/purge lines so they can't release pressure (there's a TSB on the GMT800 platform GM trucks for this one).

I'll only toss this extra bit out there because it also applies to the GM world I was in pre-Toyota from, but it may apply to other vehicles. Some vehicles have independent pressure sensors, either on the fuel pump housing or gas tank, which directly measure the EVAP system vacuum/pressure. Those sensors can slowly fail also, thus reporting bad pressure, and cause EVAP codes too; if the ECU can't properly sense how much pressure is in the system, it's probably going to think there's a leak and trigger the code.

But the gist remains the same: You popped this code because the ECU is sensing you have a leak somewhere in this system in your truck, you need to figure out why. Smoke test at the EVAP service port, and at the gas cap using a standard smoke tester attachment, should reveal where that leak is pretty quickly, if it's not blatantly obvious (loose hose, hole in canister, etc.), and just know, if you do have a loose vacuum hose, sometimes you'll hear it making a "pumping" sound when the engine is running.

​

 

Check your fuel filler neck first, mine was replaced under warranty by Toyota by the previous owner. Next check your fuel cap, they do wear out and don't seal as well after say 22 years if it's original. Fuel caps go for about $30 from Toyota, you want an OEM one since if it doesn't seal properly, it'll keep throwing CEL codes. I was getting the evap small leak on my truck and the new fuel cap has fixed it so far.

 

I got an OEM cap awhile back but it didn't fix it. Fuel filler neck is an interesting probability.

Is this the part? https://toyotaparts.ourismantoyotao...0dW5kcmEmeT0yMDAzJnQ9c3I1JmU9My00bC12Ni1nYXM=

There's a few different assemblies and parts called fuel filler neck, I'm not sure which one causes trouble

 

No, that's for your washer reservoir in front of the passenger front tire.

In the filler neck, some have used sealant (epoxy or similar) to coat the whole thing.

 

This diagram is great!

I changed the evap VSV and nothing changed. It actually got worse, popped more codes.

I went to change the CCV VSV and the bolts were so rusted I couldn't get them off. Dropped the whole evap system out. Filter was cracked, that could have been the original problem. It broke pretty easy. Looked like it was melted. Heat shield had rusted so maybe the muffler heated up the plastic.

So, my CC filter is cracked, my charcoal canister is cracked, with one bolt for the VSV broken off and the other one stuck in.

I'm wondering if it's worth salvaging or just getting the whole assembly and being done with it.

 

Doh! Thanks , I knew something ain't right hah

 

Struggling to find the fuel filler megathread referenced in some of your posts, shifty. I'm on mobile so maybe that's slowing me down.

 

https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

Goto post #2 and this section


Here is the embedded link in the screenshot
https://www.tundras.com/threads/check-engine-light-due-to-gas-cap.114959/#post-2973696

Good luck!

 

Check the vacuum lines that are connected to your EVAP purge valve under the hood near the intake manifold.

I had the same code (5VZ FE engine) and the lower hose had about a 2 inch split in it. I replaced all the crusty looking vacuum hoses I could with silicone tubing (I ordered an assortment on Amazon), deleted the codes and no pending codes so far 2 weeks later.

I also had an issue while filling gas, the pump would click off early. Hasn't happened since but I've only filled up once since I did the repair so we shall see.

 

I never had an issue filling gas, but I did replace the VSV in the engine bay and just ordered a new vapor canister assembly. The mounting bracket was so rusty I think it may have melted the plastic/made it brittle.

So, I'll have two new vacuum solenoid valves, new canister, gas cap, hoses.

Only thing left is the fuel filler neck, which I'm planning in getting too.

I want the evap codes gone so I can actually see if the CEL pops something new, rather than a longstanding CEL. This transmission code went unnoticed for awhile because my CEL is just always on from this evap leak.

I probably fucked up more shit trying to fix/find the problem but it's a part of the learning process I guess. Trying my best.

 

T

Thank you!

 

I got this EVAP canister assembly from Treasure Coast Toyota of Stuart on ebay (verified they were a real spot and they seemed legit).

Part # 77730-0C010



Installed yesterday and cleared my codes. So far so good. My truck seems to have been starting a lot quicker too. Worth the extra cost and the privilege to see when a new CEL code pops up instead of the long standing golden glow.

EDIT: by far the absolute hardest part of this was separating the special fuel line connector from the top of the gas tank. I almost gave up. Right angled pick tool and a lot of swearing got me there. Plus raining rust into my eyes lol

 

Cracked canister would definitely cause your issue. Takes a lot to crack one but it can happen. Make it 2-3 weeks of driving with no new codes and I’d be willing to call it “done”

 

It was the charcoal canister filter that seemed to be cracked.



Fingers crossed! So far so good...

I think the purge line vent hose has seen better days, I want to swap that out. Pretty much swapped all the EVAP lines in the engine. Not much left.

 

I don’t know that you can. There are a lot of fuel related lines (plastic ones) that Toyota has discontinued. Which I find so damn weird! Worth checking, but … don’t get your hopes up, and I also hope I’m wrong!

 

I was just going to pull it off, walk into a shop and get some generic fuel hose that was the right size.