Q: p0420

A vehicle with 182,000 miles is likely due for a catalytic converter. Most of the time it does mean you need a new catalytic converter. But there are a couple of other things that are prudent to take a look at. Number one, using a shop level scanner, look at the downstream O2 sensor operation. With the car running, you need to snap the throttle. In other words, quickly floor it and let off. This will inject as much fuel into the motor as possible. The O2 sensor should register this change, but not excessively. The upstream O2 oscillates between one volt and zero volts quickly, if the downstream O2 is doing the same, the catalytic converter is not doing anything. To summarize, the downstream O2 should react to a snapped throttle, but it should not spike like the upstream O2 does.

The other possibility is the PCM may need to be flashed. This will change the programming to adapt to the condition of an older vehicle. Before this is considered, you will want to perform the first procedure I outlined first. Of Course, this requires a shop level scanner, and ideally a five gas analyzer to monitor what is coming out the tail pipe. If the downstream O2 and the tail pipe emissions are within specifications, then it is time to consider flashing the PCM.

Flashing the PCM should only be done by an experienced technician. There is potential to leave your PCM dead. So it is not something even an seasoned technician should attempt without guidance from someone who has done it before. In addition, you will want to check with Toyota to see if there is a PCM update available that makes the appropriate changes addressing catalytic converter operation.

I recommend contacting customer service to see if there is a technician in your area with the experience necessary to take on this project.