# Engine code P0420 Bank 1

**URL:** <https://community.cartalk.com/t/engine-code-p0420-bank-1/56288>\
**Category:** Maintenance/Repairs\
**Tags:** rx-8, mazda\
**Created:** [October 12, 2010, 3:38pm UTC](https://community.cartalk.com/t/engine-code-p0420-bank-1/56288 "2010-10-12T15:38:22Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![map209ubg](https://avatars.discourse-cdn.com/v4/letter/m/b2d939/32.png) [@map209ubg](https://community.cartalk.com/u/map209ubg)\
**Post date:** [October 12, 2010, 3:38pm UTC](https://community.cartalk.com/t/engine-code-p0420-bank-1/56288/1 "2010-10-12T15:38:22Z")

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Is this a sensor(s) and/or the catalytic converter that needs replacement?

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**Author:** ![tardis](https://avatars.discourse-cdn.com/v4/letter/t/f0a364/32.png) [@tardis](https://community.cartalk.com/u/tardis)\
**Post date:** [October 12, 2010, 3:44pm UTC](https://community.cartalk.com/t/engine-code-p0420-bank-1/56288/2 "2010-10-12T15:44:26Z")

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Probably, but you should follow the troubleshooting flowchart for that code for your car to be certain before throwing parts at it.

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**Author:** ![mcparadise](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mcparadise/32/32_2.png) [@mcparadise](https://community.cartalk.com/u/mcparadise)\
**Post date:** [October 12, 2010, 3:44pm UTC](https://community.cartalk.com/t/engine-code-p0420-bank-1/56288/3 "2010-10-12T15:44:54Z")

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Try the O2 sensor(s) first. They are much less expensive than a new cat. There should be a trouble-shooting procedure accompanying the explanation for this code. Follow the procedure.