CAT codes thrown after fill up, things to look for? (1 Viewer)

[Chrisek]

Ever since I first purchased my 04LC in 2019 it occaisionally throws CAT codes for both banks. Always right after a fill up, usually when getting winter gas (though not always). Happens once or twice a year whether highway driving or around town stuff. If I reset the codes with Carista they don’t come back for many months. If I don’t reset the codes the CEL goes off in about 1000 miles. I have put on over 100,000 miles since purchase, any suggestions on things to check out? I replaced the fuel cap (with a Toyota OEM) right after purchasing the vehicle.
I did search but could not find any complaints centering around tanking up. Currently on a trip and will replace all 4 o2’s when I get home (over 300k miles and cannot find any records of previous replacement.).
Thanks in advance for any trains of thought to chase.

 

[Chrisek]

So today I travelled from Nebraska to Nevada. Every single fill up set it off, all winter gas as it was mid twenties at the beginning of the day for everyone.

I did stop at one point after 150 miles of driving , pulled over, turned the Land Cruiser off for 10 minutes. Restarted and continued the journey. That did not set off the codes, so the codes are only coming when I remove the gas cap (??). Not what I would have guessed. Tomorrow is a shorter day (only driving to Gilroy), if anyone wants me to try anything or check anything I’m game. Otherwise looking to head back late this week along one of the southern routes.

 

[sunfic]

did you overfill/top-off the gas tank when you fill up?

also it will be handy you have OBD code reader in the car and record the code when you have check engine light

 

[Chrisek]

I do tend to top off the tank, will stop that today and see if it helps. I do keep a carista with me. Codes are 420 and 430 and that is it.

 

[Mike NXP]

I do tend to top off the tank, will stop that today and see if it helps. I do keep a carista with me. Codes are 420 and 430 and that is it.

That'll do it. Just stop when the pump stops and don't keep topping it off. If it still happens then you can dive a little deeper.

 

[Chrisek]

So I refilled 3 times today, and all 3 times stopped when the pump stopped first time. The 420 and 430 codes came back on each time. One thing I noticed about today and yesterday (it did not happen way to Nebraska), is that the codes only come up when up to highway speeds (65mph+), never around town. For what it’s worth.
Now what is different this time (like I said earlier is this usually only happens once or twice a year), my Alternator went out and Toyota of Lincoln (Nebraska) replaced it. Obviously unplugged main battery and everything was wiped (previous navigation, stored places, radio stations, trip meters, etc). Not sure what Effect this would have, but worth mentioning. When I replaced the battery 2 years ago, it did not have this effect on the codes popping up.

 

[sunfic]

So I refilled 3 times today, and all 3 times stopped when the pump stopped first time. The 420 and 430 codes came back on each time. One thing I noticed about today and yesterday (it did not happen way to Nebraska), is that the codes only come up when up to highway speeds (65mph+), never around town. For what it’s worth.
Now what is different this time (like I said earlier is this usually only happens once or twice a year), my Alternator went out and Toyota of Lincoln (Nebraska) replaced it. Obviously unplugged main battery and everything was wiped (previous navigation, stored places, radio stations, trip meters, etc). Not sure what Effect this would have, but worth mentioning. When I replaced the battery 2 years ago, it did not have this effect on the codes popping up.

the p0420 p0430 rarely related to the fuel system. only thing I could imagine that the fuel pressure regulator may have some issue. when fuel full, the pump will have little bit higher pressure pumping the gas to the regulator, if the regulator is not working that means more fuels to the fuel injector. but usually this kind of thing will result more codes.

I suggest to install techstream to monitor the fuel trim after you fill up next time.

 

[Chrisek]

When I get home. Next week. Thank you.

 

[sunfic]

also check out this thread:

Edit: never mind yours is 04 so it is not related.

S.A.I. Modification in VVT engines to prevent its failure! Alert Alert

We've a $2.00 part in the S.A.I.S. of the VVT engine, 1s taking-out ~$7,000.00 $15,000 (inflation) in parts. WOW! I've a very easy and cheap WORK AROUND. You are going to love this ;) This thread is dedicated to the 4.7L 2UZ-fe VVT engine, in the 2006 & 2007 100 series Land Cruiser & Lexus...

forum.ih8mud.com

 

[Chrisek]

Just a quick update, today was my first fill up where the warnings did not come on.

 

[Chrisek]

I’m home (TN). Had 3 fill ups in Cali with zero codes. Then from Barstow to Oklahoma (I40) every single gas stop threw codes. Then from OK to Memphis no codes, on the final fill up west of Memphis threw codes again and left the codes on. Turned the Land Cruiser in to my local Toyota Dealer today with codes. We’ll see what turns up.

 

[BullElk]

The spark plug fouler hack has worked well at keeping CAT codes away from my '06 LX.

 

[Chrisek]

As a follow up on this, my dealer said to replace the cats, I also had them replace the O2 sensors (as far as I could tell, still had the originals at 300k miles) and did the 3 part fuel system clean. Got it back, and the LC is obviously running easier, guessing the cats were clogged and now there is less back pressure. Breezing up to 80mph much easier now (I usually cruise the LC at 75moh.
I’m back out on another lap of the country and taking the same route as the previous, currently in NorCal. No codes, no issues, but also no winter gas this trip. Won’t know for sure until next winter I think. In any case, it was a noticeable difference. Will update when appropriate with similar driving and gas.

 

[OEMGUY0720]

From the symptom you shared, my suggestion is to go ahead replace the gas cap with a new one.

 

[Chrisek]

From the symptom you shared, my suggestion is to go ahead replace the gas cap with a new one.

I put a new one on in 2019, though i agree and might go ahead.

 

[Irikumi]

I recently replaced both Cats in my 2003. Have not had anymore codes in 3,500 miles now. Get them here, only $159 each...

https://shop.exhaustdistribution.com/land-cruiser-5/

 

[Chrisek]

Got home two days ago, zero codes. At this point calling good with verification next winter.

 

[WallyZ]

Glad you got it resolved, for people reading this in the future, more than likely it had nothing to do with you filling your tank. You were probably completing “drive cycles” with the highway driving and the stopping and starting at the gas station. This link gives you an idea of what I am talking about.

Toyota/Lexus OBD-II Drive Cycles | Car OBD Diagnostics, ECU Chip Tuning & Auto Repair Support