Matsui

My 09 GX with 99k miles just had all these lights come on so I checked for the codes using the OBD tool. It came up with P0456.

Based on searching this forum it seems to be relate to evaporator leak and for most people just changing the gas cap fixed their issue. The search did not show any results for GX, but I assume it must be same for all models of Lexus.

Please let me know if you have any advice regarding this.

Also, I've noticed over last couple of months that the MPG has dropped from 18.5 to 13.5. Could this be related to the issue I'm having? Would you recommend that I just replace the gas cap or take it to the dealer to get it completely checked out?

RCsGX

Try the gas cap first. If that doesnt work take it to the dealer.


* A small leak in any of the EVAP hoses or fuel tank hoses
* A small leak in the purge valve or vent valve
* The EVAP Canister may be leaking


A 5mpg drop off is huge. Welcome to my world! I get worse that 13.5mpg around town. If 13.5mpg is your combined mpg (city and highway) something is definitely wrong!

Matsui

Yes, I'm planning to replace the gas cap first to see if that takes care of the warning lights.

I was hoping that the code would reveal the poor MPG issue. Otherwise there are endless possibilities for the cause of this. Do you think the evap leak may be contributing to this?
I'm going to start with gas cap, then check the tire pressure and air filter to rule the small stuff out. I've already added Techron fuel injector cleaner but that didn't help much.

Matsui

I replaced the gas cap and drove it several miles, but all warning lights are still on.

The code P0456 still comes up. Would you suggest resetting the code and see if it comes up again? Or should I take it to a mechanic to get it checked out. I'd rather fix an issue if there is one for peace of mind and not to harm anything further.

Please let me know what the possible causes may be. I'd like to have some knowledge prior to making a visit to the mechanic. I've searched the forum and for most people the gas cap replacement seemed to fix their issue, but unfortunately not for me.

Thanks.

RCsGX

A evap leak wont hurt your engine so Id reset it and see if it comes back. If the code comes back leave it on (dont reset it) and take it to your mechanic and have them pull the codes.

Matsui

OK, will do. Hopefully with resetting the code the "limp mode" will go away too? I don't know exactly what that is, but driving at high speed in limp mode does not sound too safe.

RCsGX

If your GX is in limp mode you wont be able to drive at high speeds because the RPM is limited. If I were youd Id leave the code and just take it by Lexus or Toyota.

Matsui

Update: I never got to resetting the code, and it eventually went away on its own + all the dash lights are now off.
I'm about half way through the gas tank and the MPG seems to be getting better so far.

Can't believe a gas cap can impact so many things.

henrylouis

Does it need a special gas cap or will any do?

Matsui

I try to avoid aftermarket parts for my GX, so I got the cap from Toyota dealer made for 5th gen 4Runner.

henrylouis

I got one today from an Auto Parts Store, it did not have the wire from the cap
to the little door.
I only drove home, so I don't know yet if it solved the light problem.

I was told Toyota could not make an extra key, so I went to a Lexus Dealer $235.00

What things can a Toyota Dealer do for me on my GX?
The Lexus Dealer is 1.5 hours away.

henrylouis

I have driven 175+ miles now and filled with gas and lights still on. Should I get a
gas cap from the Toyota Dealer since the new one from the auto store did not
solve the problem?

Kermee

iTrader: (1)

I'd go back to the Auto Store and see if they lend OBD2 units. Clear the code and see if it comes back. If it does, then I'd probably head do your Toyota dealer and have them do a EVAP check for a leak. Toyota dealership should be able to do it; Doesn't have to be a Lexus one.

Cheers,
Kermee