Catalytic Converter Questions

Hi everyone,

Last year someone stole my catalytic convertor and I had a local shop replace it. We decided to go aftermarket since OEM was so expensive. Sadly, my check engine light has been since then.

After some poking I saw that I was getting code P0420 because the voltage was fluctuating on the second O2 sensor on driver's side. As I understand it, this should not fluctuate much if the catalyst converter is functioning correctly and indeed the passenger side second 02 sensor's voltage does not fluctuate.

When checking under the care I noticed that the O2 sensor went directly to the new catalyst converter (picture attached). This brings me to my questions:

• Is this normal?
• Could I block the O2 sensor port in the new cat and put a port further back (picture attached) ?
• Would this fix my voltage fluctuations if the new cat was working as expected?

Thanks in advanced for any help.

 

Read this.

The exhaust shop fucked you, and should fix the problem they created. This is a well-known problem, on this forum at least or in the Tundra community, these trucks hate aftermarket cats. They also don't like anything but Denso brand sensors, they hate when you cut O2 sensor wires, and you can't trust scAmazon or fleaBay to get you authentic Denso sensors, sadly (but RockAuto and Summit Racing are cheaper anyhow). There's only a few brands of cats we've found in our community that won't throw codes. If you use CARB/california compliant cats, you'll have better luck.

Contrary to your information, typically my downstream fluctuate from 0.1v-0.8v on average (never more than 0.7v range), and the upstream typically sit around 3.3v on average, rarely moving once up to operating temp, never more than 0.1 at a time, if ever). This seems to conflict with what you're writing. See my ODBLink dashboards below to demonstrate that range during normal driving.

Did they cut the O2 sensor wiring with the cats?
Did you replace the sensor with anything other than Denso brand?

Make the shop fix the damn problem, you paid them to fix it, they clearly haven't fixed it, and it would appear the cat isn't compatible with the 1st gen Tundra.

Your only other option would be getting O2 foulers and installing them on the rear sensors. But fuck those people, make them do right by the money you paid them.

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