Hello,

I have a 2013 LS460 with about 134k, which I've had for 2 years. Absolutely amazing car.

A few hours ago, I was driving home, and all of a sudden, my check engine light came on, as well as a message on the dash saying that traction control was off ("TRAC OFF"). I kept a hawk's eye on the dash throughout the remainder of the drive; nothing beyond the CEL and TRAC OFF message ever popped up, and the car continued to drive beautifully. I got home roughly 16 miles/~20 minutes after the CEL had initially appeared.

After parking, I immediately start searching the internet to see what might be going on here (I would have searched something like "Lexus LS460 TRAC OFF check engine light"), and I believe the very first result was a thread in this very forum where other owners of this generation LS stated that they had gotten the same messages as a result of issues with their gas cap, such as it not being on properly.

Upon seeing this, I open my fuel door and go and check the gas cap. Lo and behold -- the gas cap is extremely loose. I tried screwing back it on in the normal direction (counter-clockwise), and oddly enough, the cap wouldn't tighten. Then, I tried turning the cap clockwise, and this actually worked when it came to tightening it, and the resulting seal seemed pretty secure.

Upon turning the car back on, I still have the CEL, but I've heard that it can take several on/off cycles after tightening the cap for the CEL to go away on its own. Of course, this is assuming the gas cap has anything to do with the CEL in the first place. I currently don't have an OBD II scanner, so I'm not able to see what codes the car would be throwing at the moment, unfortunately. I will get a scanner later today and report back as to what I find out. Thanks!

 

Loose gas cap will cause a CEL which also disables traction control. Does the cap now feel normal when you twist it tight? Sometimes the cap itself fails this happened on my Highlander, I did clear the code so not sure if it would have gone away on its own.

In case you need a replacement gas cap, 77300-52040 about $30 at any Toyota dealer.

 

Scanned the car. It's throwing up P0171 and P1170 codes, both of which seem to have to do with the air-fuel mixture in the car being too lean. Not sure what to think, honestly.

Took the car on another medium trip (30ish miles) with zero issues. As far as general performance, I got mid-20s MPG doing mixed 75% highway/25% city driving, and the car idles and accelerates smoothly. I will schedule an appointment to get the car checked out by an independent mechanic in my area ASAP and keep everyone updated. Thank you!