2018 Toyota Tacoma - P0430 Catalyst System Efficiency Below Threshold

Question

Hey guys, got a P0430 on my 2018 Taco with 70k miles. Usually, this means the cat is dead, but this truck is relatively new. I don't have any exhaust leaks that I can hear, and the gas mileage is still decent.

I used a live data scanner and the Bank 2 Sensor 2 O2 sensor is mimicking the upstream sensor, which usually points to a bad cat. However, I've heard these trucks have TSBs for software updates related to emissions. Anyone dealt with this on the newer 3.5L engines?

MisfireMatt · Answer

✅ Confirmed fix: It turned out to be an exhaust leak at the Y-pipe flange on the driver's side (Bank 2). The gasket had shifted slightly, letting in just enough fresh air to trick the downstream O2 sensor into thinking the catalyst wasn't doing its job. I replaced the crush gasket and the code has stayed off for 3,000 miles.

RustBeltRandy · Answer

Toyota released TSB-0043-20 specifically for P0420/P0430 on the 2016-2018 Tacomas. It's an ECM recalibration because the threshold for the catalyst monitor was set too tight from the factory. You likely don't need a new cat, just a software flash at the dealer.

2018 Toyota Tacoma - P0430 Catalyst System Efficiency Below Threshold

Suggest a repair