# P0420 but just replaced an oxygen sensor **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** civic, honda\ **Created:** [June 7, 2018, 1:40am UTC](https://community.cartalk.com/t/p0420-but-just-replaced-an-oxygen-sensor/118787 "2018-06-07T01:40:15Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![98\_civic](https://avatars.discourse-cdn.com/v4/letter/9/51bf81/32.png) [@98\_civic](https://community.cartalk.com/u/98_civic)\ **Post date:** [June 7, 2018, 1:40am UTC](https://community.cartalk.com/t/p0420-but-just-replaced-an-oxygen-sensor/118787/1 "2018-06-07T01:40:15Z")
2 weeks ago I replaced the bank 1 o2 sensors on my 1998 Honda civic and it took of my check engine light and then while driving and downshifting the check engine lights comes up again p0420 but says subsystem when I checked what does that mean! Look at my pics, the 2nd one is the one I have at the moment and the 1st one is the one I used to have before I changed the o2 sensors. ![20180606_203842](https://global.discourse-cdn.com/cartalk/original/2X/9/9cd9c10632b81acd51eaae5b720e12ffd0a44531.jpg) ![20180606_203824](https://global.discourse-cdn.com/cartalk/original/2X/2/2214da2bf752c27e5dbdeb8b8e57f6c03e1c66bf.jpg) ---
**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:** [June 7, 2018, 1:46am UTC](https://community.cartalk.com/t/p0420-but-just-replaced-an-oxygen-sensor/118787/2 "2018-06-07T01:46:42Z")
The code is telling you that the catalytic converter is no longer doing its job. Tester ---
**Author:** ![98\_civic](https://avatars.discourse-cdn.com/v4/letter/9/51bf81/32.png) [@98\_civic](https://community.cartalk.com/u/98_civic)\ **Post date:** [June 7, 2018, 1:53am UTC](https://community.cartalk.com/t/p0420-but-just-replaced-an-oxygen-sensor/118787/3 "2018-06-07T01:53:54Z")
Thank you so now I just replace it then? ---
**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:** [June 7, 2018, 1:56am UTC](https://community.cartalk.com/t/p0420-but-just-replaced-an-oxygen-sensor/118787/4 "2018-06-07T01:56:34Z")
Yep! And here’s where you start. [https://www.rockauto.com/en/catalog/honda,1998,civic,1.6l+l4,1315633,exhaust+&+emission,catalytic+converter,5808](https://www.rockauto.com/en/catalog/honda,1998,civic,1.6l+l4,1315633,exhaust+&+emission,catalytic+converter,5808) Tester ---
**Author:** ![98\_civic](https://avatars.discourse-cdn.com/v4/letter/9/51bf81/32.png) [@98\_civic](https://community.cartalk.com/u/98_civic)\ **Post date:** [June 16, 2018, 1:06am UTC](https://community.cartalk.com/t/p0420-but-just-replaced-an-oxygen-sensor/118787/5 "2018-06-16T01:06:10Z")
Fixed the problem I replaced my whole catalytic converter with the intake manifold and the check engine light went away thank you