Celica Forums General Discussion Engine and Performance Multiple Evap trouble codes, need some help or info.

Hello all, I'm posting here hoping to find some Celica and Toyota specific knowledge. The vehicle in question is actually my girlfriend's, a 2002 Celica GT. She has her inspection coming up and the car is throwing some trouble codes. P0171, P0440, P0441, and P0446 are all the codes I'm getting. I've cleared and re scanned the car at least 3 times and the codes are consistent. I really don't have a large knowledge or familiarity on these cars because I've never owned one. All i know is that it's a 1.8l, it has 258,xxx miles, smokes a bit and leaks a bit of oil, but otherwise is a good running car. It came with an aftermarket intake and a straight pipe after the cat. Now I know off hand there's some sort of evap or vacuum line disconnected by the intake, and when I noticed and tried to hook it up it made the car want to barley run, so I left it as is. I'll try to get some pictures. Just wondering if off those sets of codes anyone would be able to point me in the right direction. Looking into the codes only gave vague results all essentially saying the same thing in different ways. Any help would be greatly appreciated

2002 Celicas typically burn oil, not leak it, this is what causes the Evap codes due to fouling of catalytic converter.

Only true fix is to replace piston rings or engine altogether and catalytic converter.

To pass inspection, reset Codes and put through drive cycle until all bit Evap monitor restored and hopefully no codes.

May need to use a spacer or spark plug non fouler on the downstream O2 sensor.

That entire thread never comes to a definitive resolution. Charcoal canister, VSV, hoses, gas cap, replace cat, O2 sensors, purge solenoid, flush this and that.

I spent 750$ at the dealer for this issue with no success.

I went back to the dealer for this issue and was quoted 5K for replacement of entire exhaust system.

Or you can spend 45$ for a OBD2 scanner, 10$ on a spacer, 10$ for an O2 sensor socket and save a fair bit of grief.

Been driving 7 years since, no issues.

The P171 System lean bank 1 means too much air, not enough fuel, usually caused by a dirty or bad Mass Airflow Sensor, the trapezoidal part on the big air intake hose right behind the air filter box, held down by 2 small philip screws.

Swap in a known good MAF sensor from another Toyota or Lexus to see if that fix the problem. All Toyotas and Lexus use the same MAF made by Denso. If that solves your problem then replace with a new MAF, or clean the old one with non-residue contact cleaner spray sold in Walmart.

if that did not fix the problem then there may be air leaks on air hoses or vacuum lines around the throttle body or the airbox. If one of those little black rubber hoses are not hooked up tight or cracked, it will pull the P171 code.

The 400s codes have to do with the evaporative system, recirculating gas vapor from the charcoal canister on top of the gas tank to the throttle body for burning. After 150K miles, the canister is likely broken, not holding gas vapor and needs to be replaced.

At 250K miles, my GTS had those codes. I bought an used canister on eBay for $100. It came with a solenoid, switch and hoses. One hour labor $80 to install and those codes were fixed. The car would have to be on a lift for access to the gas tank. It's not convenient or safe to get under the car on jack stands.