# Would my car pass emissions straight after having my cat replaced? (Code p0420) **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** toyota, camry\ **Created:** [November 12, 2022, 1:54am UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379 "2022-11-12T01:54:37Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 13, 2022, 8:02pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/21 "2022-11-13T20:02:01Z")
> [@nickc498](#): > > using a gallon of fuel injector cleaner and driving on the highway for 30-45 minutes. He said he’s been able to get hundreds of vehicles to pass emissions that way. That might work for an HC emissions (tail pipe hydrocarbon emission test) failure, or maybe even for CO or NOX tail-pipe problems; but I’m guessing that method wouldn’t help w/the cat or evap system. I’ve used fuel-system chemical cleaning to assist my Corolla to pass Calif’s HC spec. It does seem to help improve the tail pipe measurements slightly. For a 2000 model year, may not even require tailpipe tests. I don’t think the oil consumption is what damaged your cat. Aftermarket gadget, so It may have just pooped out with 3 years of use, or more likely, there’s some sort of fuel mixture problem. ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 13, 2022, 8:55pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/22 "2022-11-13T20:55:09Z")
I was told that my engine is burning oil and that’s what damaged my cat. As far as I know, the car doesn’t have an EVAP problem. I believe it just switched to not ready after I cleared the P0420 code. Instead of using fuel injector cleaner, I’ll try Pure Lacquer Thinner. Scotty Kilmer recommends this specifically for the cat/P0420 code. I’ll just give it a shot and let you all know how it goes. If that doesn’t work, Scotty recommends disconnecting the cat and letting it soak in water and detergent overnight. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 13, 2022, 9:07pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/23 "2022-11-13T21:07:09Z")
> [@nickc498](#): > > the car doesn’t have an EVAP problem Sorry, misunderstood the EVAP issue isn’t an actual EVAP system failure, but that the EVAP readiness monitor is not complete. Once you get it set to complete, be sure not to disconnect the battery or clear an evap diagnostic code with a scanner, b/c that will set it back to incomplete. No experience with the water/detergent soaking the cat technique, but I’m guessing that is likely just wishful thinking, will take a lot of time & effort with little chance of gain. The fuel injector cleaner seems worth a go, doesn’t cost much or take much time, and might help. Plus your fuel injectors will be cleaner in any event. I’d recommend a fuel trim test. Not overly expensive, done w/a shop scanner is all. Once you get the results , post them here for more ideas. Best of luck. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [November 13, 2022, 9:17pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/24 "2022-11-13T21:17:35Z")
Instead of listening to some bad recommendations from off the internet, why not use a product that’s formulated to try to resolve cat problems? ![image](https://global.discourse-cdn.com/cartalk/original/3X/f/5/f549749605bd186a2cc2fc1ffd2c29533523ba04.jpeg) ![image](https://global.discourse-cdn.com/cartalk/original/3X/7/e/7e747afb3edf93e443671191b08f7cffa4ce57ce.jpeg) Tester ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [November 13, 2022, 9:21pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/25 "2022-11-13T21:21:30Z")
> [@nickc498](#): > > Instead of using fuel injector cleaner, I’ll try Pure Lacquer Thinner. Scotty Kilmer recommends this specifically for the cat/P0420 code. I don’t know any real vehicle mechanics that would even ask Scotty Kilmer the time of day . ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 14, 2022, 8:03pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/26 "2022-11-14T20:03:42Z")
I’m also going to try changing the PCV valve. I heard that this can also stop the engine from burning oil. Which one do you guys think I should get? ![Screenshot_20221114-135610_Samsung Internet](https://global.discourse-cdn.com/cartalk/original/3X/4/8/48edeef2c900eb7d01aa9b19fcddaea140a2d0e7.jpeg) ![Screenshot_20221114-135553_Samsung Internet](https://global.discourse-cdn.com/cartalk/original/3X/4/1/41dc48d5d5f97b527dd9e36235dc33a60915ea31.jpeg) ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 14, 2022, 9:24pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/27 "2022-11-14T21:24:16Z")
As long as both are spec’d for the engine, threads correct etc, I’d choose the top one myself. PCV valve’s are pretty simple devices and are not a common failure item by reports here. They are designed to only pass a small amount of flow at engine idle, but more flow at higher rpms. Inside there’s just a spring, valve, & seat. Both my Corolla and truck use a slightly different style, held to engine by a grommet only. To test I just pull the hose and PCV valve from the grommet, keeping PCV valve attached to hose, and make sure I feel a robust vacuum from the end of the valve when the engine is idling. I also test by shaking. If shaking doesn’t produce a noticeable rattle I’ll either clean it or replace. I think in 50 years of diy’er maintenance, I’ve only had to replace one PCV valve. In that case valve was allowing too much air to pass at idle, creating vacuum leak symptoms. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [November 14, 2022, 9:54pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/28 "2022-11-14T21:54:10Z")
> [@nickc498](#): > > I’m also going to try changing the PCV valve. I heard that this can also stop the engine from burning oil. A gunked-up PCV valve can definitely increase oil consumption, so installing a new one–coupled with cleaning out the hose leading to the PCV valve–is a good idea, and may help to a certain extent. But, as to stopping a badly worn engine from burning oil… no. 🤔 ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 14, 2022, 9:59pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/29 "2022-11-14T21:59:21Z")
I agree. It’s worth a shot. How do I go about cleaning the hose leading up to the PCV valve? ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 14, 2022, 10:08pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/30 "2022-11-14T22:08:33Z")
Is there any reason in specific why you would choose the top valve? ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 14, 2022, 10:09pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/31 "2022-11-14T22:09:15Z")
Less expensive. ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [November 14, 2022, 10:16pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/32 "2022-11-14T22:16:23Z")
Won’t the Rock Auto part have a shipping charge ? That might make the local Autozone part less costly. ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 14, 2022, 10:19pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/33 "2022-11-14T22:19:21Z")
Yes, you’re 100% right about that. I’m going with the AutoZone part. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 14, 2022, 10:30pm UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/34 "2022-11-14T22:30:53Z")
When you go to AZ, show them the ad above for the less expensive part from Rock Auto. They might match the RA price. ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 15, 2022, 1:18am UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/35 "2022-11-15T01:18:30Z")
Hey, what size ratchet and socket do you guys think I should get for replacing the PCV valve? ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [November 15, 2022, 1:21am UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/36 "2022-11-15T01:21:09Z")
> [@nickc498](#): > > Hey, what size ratchet and socket do you guys think I should get for replacing the PCV valve? When you buy the part if there is a Harbor Freight or Ace Hardware close you can find what you need to fit . ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 15, 2022, 1:35am UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/37 "2022-11-15T01:35:36Z")
I have the part and Im on my way to Walmart. Any suggestions? They usually have everything behind glass. ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 15, 2022, 2:43am UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/38 "2022-11-15T02:43:12Z")
I’m a newb. Should I get a 1/4 or 3/8 ratchet? ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [November 15, 2022, 2:53am UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/39 "2022-11-15T02:53:31Z")
3/8" ratchet. Looks like 17 mm, get a set of deep sockets that include 17 mm or a set of metric wrenches. ---
**Author:** ![nickc498](https://avatars.discourse-cdn.com/v4/letter/n/838e76/32.png) [@nickc498](https://community.cartalk.com/u/nickc498)\ **Post date:** [November 15, 2022, 7:07am UTC](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379/40 "2022-11-15T07:07:01Z")
Good news, guys! I cleared the P0420 code and then I tried Scotty Kilmer’s method for cleaning the catalytic converter (using a gallon of Lacquer Thinner and driving 150 miles at highway speeds). My check engine light didn’t return for the entire 150 mile ride! In the past the CEL would always come back on within 20 miles of driving. The Catalyst monitor is still not set though. I’m guessing that the PCM is still running tests? What are your guys’ thoughts? As soon as that monitor is ready, I’m going for inspection. [Previous page](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379.md?page=1) [Next page](https://community.cartalk.com/t/would-my-car-pass-emissions-straight-after-having-my-cat-replaced-code-p0420/187379.md?page=3)