Wondering if anyone can give me some information for a 2001 Lexus ES300 on a P0442 code. Computer scanner reads off Evaporative emission system leak detected (Small leak). First code that I had was a P0440. I replaced the old gas cap with a new one. Code was cleared never came back. 3 weeks later the engine and traction control light came on and has been on for two days now with P0442 code. Checked all my vacuum hose lines for any cracks which were all replaced this August of 2020. All the hose lines are still good. The engine does start well at first start up. If I turn it off after 5-10 minutes of drive time then start back up the engine will idle low, rough, sputter, and at times will stall out. Any other ideas of how to fix this issue? I’ve thought about checking and replacing the canister purge valve and solenoid.

 

Hello,

What vacuum hoses did you use for the repair: Metric (3.5, 5.5mm), or Imperial (5/32, 7/32in)? 5/32in (3.9mm) is a tad bit bigger than it should be, hence if hoses are not the best quality, they may start to develop some leaks. For 3.5mm hoses, I would suggest buying Toyota 90999-92003 hose, its cost is pretty much on pair with aftermarket brands, while there is nothing that can beat Toyota OEM hoses in terms of quality. As for the 5.5mm hoses, it is a bit trickier, I have yet to find OEM ones separately, that said, good quality 7/32in (5.56mm) hoses should also work just fine, since it is pretty much on target. The same goes for aftermarket gas caps, they are not always the best, FSM even advises to throw them out in favor of OEM ones.

P0442 code indicates a small leak in the system, it may be tough to diagnose just by looking at hoses. For now, try resetting the code by unplugging the battery for a few minutes, while at that, make sure the cap is tightened. See if the code will return, if so, check Vacuum Switching Valves, which have a tendency to "hang" in the open position. To test them, attach the hose to one of the outlets and while blowing in it, add power to contacts, see if the routing of the solenoid will change. It may also be a good idea to go for a smoke test and see if you will be able to spot any leaks. Good quality smoke machines can tell how much smoke escaped during specific amount of time, which can tell how big the leak is. If there are no leaks at all, check the Pressure Sensor located near the Charcoal Canister.

Hope this helps and best of luck!

 

Thanks for the suggestions. I have had the same PO442 leak forever.

 

so check your two larger hoses. They do crack over time. The one from air box to throttle. Quick way of looking for leak is spray brake clean