# 08 check Malibu catalytic converter issues **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [September 22, 2017, 4:10am UTC](https://community.cartalk.com/t/08-check-malibu-catalytic-converter-issues/107989 "2017-09-22T04:10:09Z")\ **Posts on this page:** 1\ **Showing post:** 7
**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:** [September 23, 2017, 10:33pm UTC](https://community.cartalk.com/t/08-check-malibu-catalytic-converter-issues/107989/7 "2017-09-23T22:33:46Z")
Informative post there TSM 🙂 For the OP, here’s the link to what the waveforms look like on the scan tool when a shop tests a cat. > [@Has my Catalytic Converter gone bad and is it worth it to replace it?](https://community.cartalk.com/t/has-my-catalytic-converter-gone-bad-and-is-it-worth-it-to-replace-it/107714/2): > > p0420 is reduced catalyst efficiency - that doesn’t always means the cat is bad, especially when you have a misfire. P0502 is the vehicle speed sensor which should have no effect on misfires.problem or take it to So to answer your questions, Yes, use a pressure tap into the forward O2 sensor and run the engine open loop to check backpressure You have several places to insert the pressure taps, test, and decide which cat is clogged, if, in fact, they are. No, this is time for you to properly … --- _[View the full topic](https://community.cartalk.com/t/08-check-malibu-catalytic-converter-issues/107989)._