AtomicAWD

I had a full cat-back (no secondary cats) put on Tuesday and today we're getting snow so I'm using the "snow mode" button, and the light came on. Car has 64,000kms and I had it in for service/inspection a month ago. Any immediate ideas what it might be?

Sasnuke

Without the code it could literally be anything.
Because the catback installs after the last sensor, the computer shouldn't know anything is missing, so likely the exhaust has nothing to do with the code...just coincidental.

Maxxxx

I scared myself the same way when I just got my midpipe...turned out the gas cap was loose loll

AtomicAWD

Was hoping it might be something obvious, but I imagine it probably won't clear until done so manually. Can anyone with a reader check and reset it, or do we have to go to Lexus and fork over for them to do it?

Maxxxx

HOMER350

The cheapest scanner I have was less than $20 us . It will read the code and you can look it up on your own, and allow you to clear the codes. Let us know what you find.

AtomicAWD

And suddenly... the light goes out.

Sasnuke

Theory: Gas cap was loose, light came on, likely P0442 code.
You tightened cap, after a few times of the EVAP self test running and confirming system was sealed, code cleared.

Just my theory...it's happened before.

AtomicAWD

Could be, although the timeline:

Mon - gas
+~100kms
Tues - install exhaust
Fri - check engine light comes on
Fri - gas
+~100kms
Mon - check engine light goes out

Sasnuke

Possible it could have been the gas cap depending on the temp outside.
I can't remember the exact temp, but I think once ambient temp is below 5C, then the EVAP self test won't run.
I could have the temp wrong, but for sure there is a minimum threshold that the EVAP self test won't run...and it's when it's cold out, not hot.

So it's possible if it was cold enough on Tuesday and Wednesday, maybe Thursday too, then the EVAP self test would not have run.
If it ran Thursday night or Friday, that could have triggered the light.
Then after the cap was tightened on your Friday fillup, the test ran over the weekend and found the system sealed, and the light cleared Monday.

HOMER350

Can't it be scanned and still show a code in the history for X amount of miles? Now that won't show up on a $20 scanner but an auto parts store or my OBDLinks I believe would show some code history.

Sasnuke

Yep...totally possible it will show up as a History code.

AtomicAWD

I'm just glad that it cleared itself as I was expecting it to stay on once triggered and require manual clearing ($).

AtomicAWD

Aaaand, it has returned. Would one of these get the codes read? Should probably get one eventually anyway.

Flash5

I would recommend the Lemur Blue Driver Bluetooth OBDII. It's awesome! It even tells you the most common fixes for the code etc.