"Trac Off" & "Engine Check" - gas cap loose?

Just spent a few hours worrying about the "Trac Off" & "Engine Check" lights that suddenly appeared on my 2012 4cyl Tacoma today. Spent an hour searching the messages here, pointing to various possibilities (MAF sensor or hoses, O2 sensor, tire size changes, EVAP cannister, fuel cap loose?). Then I finally hooked up my OBD dongle, to check the code: "P0456 EVAP minor, check fuel cap &c"

Unscrewed & re-screwed my fuel cap, cleared the OBD code, now OK (no faults).

I can't imagine why the "Trac Off" light should be triggered by this "problem", nor how much worry, effort, hours and money has been spent looking for the solution to this apparently common problem.

Bottom line: get a cheap bluetooth OBD reader (<20$ on Ebay). Check the codes, you may find a quick & cheap solution to your problem!

 

CEL = Always check gas cap.

 

Yep.. first thing to check. Have had to R&R 3 in 12 years.

 

I really wanted a locking gas cap when I first got the truck but when I got it for some reason it seems like it was not compatible and I always got a check engine light so eventually I got rid of it.

 

Chinese junk.

 

Had this same thing happen yesterday. Pulled the code, and it was gas cap. Disconnected the battery and reset it (after tightening the cap). I still am unsure why the trac light comes on, but there was an answer in an older thread I think.

 

So this keeps happening and I keep resetting the ECU (removing the negative and waiting, then reconnect) it stops the CEL for a bit but then it comes up again. I replaced the cap. The only replacement I could find that was not OEM was the Stant non-locking. Reset the cel. Drove it for a day and it popped the came CEL again. Any thoughts on what else I can try? The computer is saying gas cap.

 

I believe that I read somewhere, that any CEL will also trigger Trac Off.

 

When you get the CEL for the Gas Cap it isn't specifically the gas cap causing it. The CEL is for an Evap Emissions Check for leaks in the system. The Loose gas cap will cause a leak, but it isn't the only source for a leak.

Common Areas for a leak from the service manual:

• Fuel cap (loose)
• Leakage from EVAP line (Canister - Fuel tank)
• Leakage from EVAP line (Purge VSV - Canister)
• Canister pump module
• Leakage from fuel tank
• Leakage from canister

 

Any ideas on how to test for the leaks myself or is this a dealer/shop kind of operation? After a reset I wait a few cycles and the CEL pops again. So I am guessing the problem is something more than just the cap.

 

2012 Tacoma I see. But a 4 cyl. Be glad it wasn't the dreaded...............
P2440 and P2442 Codes

That fault is a $2,000 fix a plagues the 2012 models. There are several Threads on here about it.

 

My Trac Off and CEL are on permanently due to Long Tube headers from URD. O2 simulator doesn't work on 2015's.

 

Any good shop can do a smoke test on the evap system to locate the leak.

 

Quit blaming everything else when Toyota is the problem......if the truck had a locking fuel door, we would not have to deal with locking gas caps....

 

Thanks everyone for the great info. A few months ago I put a Stant locking gas cap on my 2012 SR5/V6. Two days ago I got the check engine/trac off lights. If it wasn't for this group I would never have thought it was just the gas cap. Put the original cap back on this morning before making the drive to work, both lights still on. Started the truck up after work and no more lights! I would have thought only the check engine light would be activated with this, not the trac off?! Also wonder why no issue for the first few months I used the locking cap. Anyway, thanks guys!

 

Aftermarket gas caps are garbage.

 

Yeap,I had too go back too a factory cap after putting a locking cap on and getting a trac off ,check engine light.Those aftermarket caps are all made in china abd simply do not work well with Tacoma trucks.

 

Are yall ready for SCIENCE?? ...the traction control shuts off when a problem with the engine is detected to prevent a situation where you spin out, the computer cuts engine throttle, and the engine dies cause it has previous problems. Now you are stuck in front of oncoming traffic with a dead engine and fresh poop in your fruit of the looms.

Also, just so you know. The stock cap is regulated to keep negative 7 psi in the fuel tank. An electric motor pulls a vaccuum on the tank and the cap regulates it. Then the evap system vents it to the charcoal canister on the top of the tank. Thats the answer I got from toyota corporate when modifying my fuel system for deep water.