Engine check light - code p0442

A check engine light appeared on my 02 3.4l taco. Code is p0442. Stated it’s a EVAP System leak detected. (Small leak) states the most probable starting with, gas cap, evap canister, fuel filler neck, evap canister vent solenoid, fuel tank, evap line, evap purge solenoid valve. Has anyone dealt with this same code? If so what do you recommend to do? I’m not sure where to start so any advice would be great! Truck still running great and the lights been on for a few days now.

 

Start with the free or cheap stuff. Check gas cap o ring, clean mating surface and lube o ring with silicone lube. Look for leaks in filler neck and associated vac lines. After that, may need to pay a shop to do a smoke test to find the leak. Alternatively maybe you’ll get lucky and smell gas fumes coming from a specific spot, then notice an obvious leak that you can fix. Beyond those options, it generally starts to get expensive to diagnose and repair, since many shops will automatically put a new evap canister without knowing the root cause.

 

Find a shop that will smoke test the EVAP system. There is a green port on EVAP hose to plug in a smoke machine.
Once you find the leak repairs begin.
A new OEM gas cap and cleaning the sealing surface on filler neck does the trick sometimes.
Other times the gas tank needs replacing.

 

+1 on fixing/replacing the cap. Fixed it for me. Also keep in mind you need to reset the ECU or let it run 3[?] heat cycles to drop the code.

 

Replace that cracked and dry rotted vacuum line and you should be good

 

The P0442 could be one of the most frustrating codes to fix because it could be so many things. Start with obvious like the gas cap, beyond that don't waste money on parts and get it smoke tested. In my case it was some little vac line that was cracked. I would have never found it without the smoke.

 

Thanks for the input guys. I’ll start with an oem gas cap. And what vacuum line is being talked about that cracks and needs replaced? And what is the best way to clean the filler neck?

 

Should be an emissions sticker under the hood showing all the EVAP hoses.
A thickwall Silicone hose kit is well worth the price. A Dremel and brass wire wheel saves time and elbow grease cleaning the filler but a scrubbie works too. The Oring in the gas cap is availabe replacement part. Purge Selnoid is usually P0446 but here's the FSM test info.

 

Emphasis on brass wire wheel if you use a dremel at the filler neck. Even then, brushed motors, like those on a dremel, can generate some sparks, but maybe I’m just paranoid. Scotchbrite pad works fine.

 

Revival. This thread came up while searching, figured I would add to it.

P0442 came up along with fuel smell in between cab.

Looked at top of tank and saw the gaskets were cracked. So I ordered and replaced those by dropping the tank. Visually inspected lines and felt confident to reinstall.

Code came back. Meh, bought a oem gas cap since o ring looked tired.

Code came back. Ok smoke machine time. Ordered one off Amazon.

$186 ANCEL S100 Automotive Smoke Machine Leak Detector, Pipeline Fuel Leakage Detector Compatible with 12V Cars, Trucks, Motorcycle, ATV, Boats, Snowmobiles

https://www.amazon.com/gp/aw/d/B09R44F4JV?ref=ppx_pop_mob_b_asin_title
Cool little unit runs on Johnsons baby oil and 12 volts. Has the hook up for evap test port and Schrader valve tool (Schrader valve on evap is backwards, turn clockwise to loosen).

Pretty easy, hook up the machine as directed on box, gently pinch off the fresh air tube with vise grips (about 18mm o.d. hose from charcoal can runs up to filler neck) and put the smoke into test port. Within about 1 min I noticed smoke between the cab. Got under it with mirror and saw it coming out the top of roll over valve. Ordered and replaced that today. Cleared code, will see how it goes and test again if need be.

 

Forgot to mention I tilted the bed up to change the roll over valve. It was much easier and quicker than dropping the tank.

If you have a double cab and need to change fuel pump/gasket, I think dropping the tank is the way to go since cab sits over that part.

Otherwise tipping the bed was easy.
Remove gas cap.
Loosen 3x 17mm bolts on passenger side (5 ft short bed)
Remove 3x 17mm bolts driver side.
Use a pry bar and various size pieces of wood to slowly raise the bed.
Check height with new valve to make sure you have enough clearance to get the old valve out of tank.
Use short pry bars/ screw drivers to lift out old valve.
Remove 1 easy vacuum line
Remove the larger line. Its clip can be released with small Chanel locks by squeezing the part closest to the R/O valve to release its teeth that bite the lip. With teeth released, pull the line off.
Change seal.
Use dielectric grease or similar lube to help new R/O valve get into gasket.
Reassemble in reverse order.

Note you may need to disconnect tail light wires if you are changing more parts on a 6ft bed. I did not have to.

 

Been fighting the P0442 code for some time. I replaced the gas cap with new factory gas cap, code came back, replaced gas cap again with another new Toyota cap hoping the first one may have been a dud. Code still coming back so ordered smoke tester and ran smoke in the system, smoke coming out of the gas cap. Filler neck has been cleaned multiple times. No smoke coming from anywhere else in the system. Does this filler neck ever need to be replaced due to threads holding the cap being worn?

 

Maybe double up on the o-rings. Take the one off the other cap & put a lot of silicone grease on it.

At least you found the leak. I wouldn't think the 'threads' can wear out. It is plastic & rubber on metal, after all.

Good luck!

 

Crazy! Inspect the filler neck for any irregularities. Maybe a small rust hole or mud is on the sealing surface. Maybe there is a crack below the sealing surface under the flange. Try using a small flash light to see any light through the tube.

Good luck!

 

Damn, I’ve been dealing with this code for a while too. I also bought a new Toyota gas cap but didn’t even consider that the leak might still be there!

 

Replaced the filler neck with a new Toyota one and it still smokes from the same spot. Is it possible there some allowance of vapor that can be coming out of the neck, like from a vent, and the the actual leak is somewhere else? You all running smoke in the vac lines with the truck off, idling cold, or idling warm?

 

Ran smoke in the Evap test port near brake master/battery. Truck was off.
There is about a 18mm rubber vent line under the bed that connects to the filler neck. It needs to be clamped off to do the test properly. It comes off the charcoal can if memory serves right.

 

got a pic of this rubber line by chance?

 

I used long nose style vise grips with a rag to gently clamp it closed.

 

Pinched that line, no smoke anywhere. The end of the line by the can looks beat up, so I put a clamp on it, cleared the code and proceeded to jump in the pool. Will see.