Review on 🚀 Denso 234-4163 Oxygen Sensor: High-Performance Monitoring for Optimal Engine Efficiency by Jasmin Rojas

The check engine light for my 2003 Sienna came out two months ago with code P0420. I cleared the code twice and each time the light came back after 200-250 miles. P0420 indicates a catalytic converter malfunction. The computer "knows" this by tracking the output of the sensor (bank 1 sensor 2 on the Sienna) after the cat, and can be fooled by a bad sensor. Since the sensor is more likely to fail than the cat itself, replacing the sensor would be the natural first attempt to fix the problem. The sensor was easy to swap out. The only tricky part was loosening the two 12mm nuts. I partially rounded one because my 3/8" socket and ratchet didn't fit at a 90 degree angle on the nut due to the limited space. My 1/2" socket and ratchet fit fine. I pre-sprayed a PB Blaster and used a tube to increase the torque. Removing the passenger seat (fixed with 4 screws) made it easier to disconnect and connect the cable. The sensor voltage is now about 0.7 volts and the two air/fuel mixture sensors are about 3 volts, all normal. The check engine light did not come on after 400 miles and counting. (Update January 15: 2000 miles and invoice.) Update September 16: Check engine light has come back with code P0420 a few times since I replaced the sensor. Each time I cleared the code and did nothing else. I think the shortest amount of time the light came back after resetting was about 500 miles and the longest was about 8000 miles. Anyway, searching the internet shows this to be a common problem, especially for 2001-2003 Siennas. The real problem lies with the ECM, which has an overly strict hard-coded threshold that can easily be reached as the catalytic converter and/or O2 sensor become less efficient (but efficient enough to control emissions). Toyota has released an updated ECU to solve this problem. ECU replacement costs over 1000 which I wouldn't do for such an old car. Replacing the cat with an OEM cat costs about $500 just for the part, which I'm also reluctant to do, and a non-OEM cat won't solve the problem. So I'll just clear the code and hope the check engine light doesn't come on too often.