Persistent P0037 Code

[Hamdhan777]

Hi guys,

I have a 2009 Toyota Yaris 1.33 TR. A few weeks ago the engine management light came on. I plugged in my OBD2 reader and P0037 was shown.

Thus, I took my car to the garage, who recommended I replace the post-cat O2 sensor. After replacing it, they found that the P0037 error code returned. Suspecting a faulty sensor, they replaced the rear O2 sensor again. Still, same issue.

Then, I took my car to a Toyota dealership, who said the front sensor also needed replacing as it was not sending the correct voltages. Thus, I have now replaced both pre and post cat O2 sensors. But, P0037 returns as soon as the engine is warmed up.

I always ask for the removed parts back. It appears that the previous owner installed the pre and post cat sensors the wrong way around. Strange given that the vehicle was running fine for the past 2 years.

Thus, I am now quite confused. I have new pre and post cat sensors, but the P0037 will not go away. Any advice is appreciated.

Thanks,
Hamdhan