Skip to content
View in the app

A better way to browse. Learn more.
Ford Owners Club - Ford Forums

A full-screen app on your home screen with push notifications, badges and more.

To install this app on iOS and iPadOS
  1. Tap the Share icon in Safari
  2. Scroll the menu and tap Add to Home Screen.
  3. Tap Add in the top-right corner.
To install this app on Android
  1. Tap the 3-dot menu (⋮) in the top-right corner of the browser.
  2. Tap Add to Home screen or Install app.
  3. Confirm by tapping Install.



Join the Independent Ford Owners' Club

Our community has been built by enthusiasts, for enthusiasts, and proudly run by Ford owners' for over 18 years. As an independent, non-official club, everything you’ll find here, advice, support, and opinions, comes directly from members with genuine Ford ownership experience.

Join our friendly community... it's Free!

 

p0420 dtc only when running in LPG

mattuz
mattuz
in Ford Fiesta Club

Featured Replies

Hello everyone,

My 2019 Fiesta 1.1 75hp with factory-fitted LPG recently started throwing the check engine light with DTC P0420. However, this does not happen (as far as my small test showed) when running on regular gasoline.

I recorded a short trip using FORScan and noticed that the catalytic converter's O2 sensors show almost identical values all the time, which suggests a bad catalytic converter. But then a question comes to mind: if the catalytic converter were truly faulty or no longer working, why does this only happen when running on LPG? As far as I know, LPG produces fewer emissions than gasoline, so the DTC should either be triggered when running on gasoline or on both fuels.

Do you have any suggestions? I also checked the fuel trims, but I'm not an expert—maybe you can take a look.

In order from top to bottom: O2S1, O2S2, fuel type, fuel level, lft, sft.

image.thumb.png.2bd2bad50c73a9fea7bcb807741d3073.png

  • Quote


    • Latest Deals

    Ford UK Shop for genuine Ford parts & accessories

    Disclaimer: As the club is an eBay Partner, The club may be compensated if you make a purchase via the club

    Join the conversation

    You can post now and register later. If you have an account, sign in now to post with your account.

    Guest
    Reply to this topic...
    Go to topic listing

    The "Digestive"

    • The Digestive Forum Roundup (24th May - 31st May 2026)

      Steve ·
      The Digestive Forum Roundup (24th May - 31st May 2026) We hope this email finds you well and enjoying your week. As always, our forum has been buzzing with activity, so we’ve compiled the highlights for you. Plenty of interesting discussions are taking place, especially around the Ford Focus and Fiesta models. Starting off with the Focus, many members have been discussing issues with the Emergency Call System, particularly in the Mk4 model. PLB raised concerns about persistent malfunctions, a se
      Steve
      Steve
      • 120 views





    Background Picker
    Customize Layout

    Account

    Navigation

    Search

    Search

    Configure browser push notifications
    Chrome (Android)
    1. Tap the lock icon next to the address bar.
    2. Tap Permissions → Notifications.
    3. Adjust your preference.
    Chrome (Desktop)
    1. Click the padlock icon in the address bar.
    2. Select Site settings.
    3. Find Notifications and adjust your preference.