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!

 

Lambda / Oxygen Sensors On A 2004 Fiesta (Help Please :) )

JNY12
JNY12
in General Ford Related Discussions

Featured Replies

Hi there,

Hopefully some of you smart people will be able to help me...

I have an engine warning light on and got it diagnosed with the following code...

"P0030 H02S Heater Control Circuit Bank 1 Sensor"

I understand this is the lambda sensor that needs replaced but I don't know if its the upstream or downstream sensor from the CAT. How would I know which one needs replaced other than try both when replacing? Also, is there a difference in sensor between front / back sensors i.e. could I buy the wrong one? Looks like they are both 4-pin.

Thanks in advance :)

  • Quote


    This doesn't necessarily mean the sensor is at fault, it could be an electrical issue elsewhere.

    The code is referring to bank 1 sensor 1 so it will be the precat sensor.

    Be vary of cheap aftermarket universal sensors, they are usually rubbish.

  • Quote

    I think that bank 1 refers to 'header' 1, where in a v6 there is 2 headers if that makes sense?

    It's sensor 1 or sensor 2 you need to worry about.

  • Quote
    • Author

    Thanks for advice guys. Anyone got any recommendations for sites to buy from - I'm from Glasgow and have bought from EuroCarParts before and they seemed ok (not sure how pricey they are in comparison though). And are both pre/post CAT sensors the same part? Thanks

  • Quote

    Thanks for advice guys. Anyone got any recommendations for sites to buy from - I'm from Glasgow and have bought from EuroCarParts before and they seemed ok (not sure how pricey they are in comparison though). And are both pre/post CAT sensors the same part? Thanks

    ECP are generally ok, some of the stuff they sell is quite poor though so just be aware of what brands you are buying.

    NGK, Bosch or Denso stuff should be of good OE quality.

    the sensors may well be the same although i wouldnt have thought the rear one would be heated - the front one is heated as it will only work when above a certain temp, the quicker it gets there the more efficient the engine will be. i suspect the electrical connectors will be different though

  • Quote

    I got my Lambda sensor from Partco behind the Kelvin Hall last year. It was an NGK and cost £57. No issues with it.

  • 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
      • 196 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.