Q: Q: p0420

asked by on

i have a p420 , i know that the p420 has to do with the catalytic converter..but by replacing the catalytic converter will erase code p420 or there are other problems that might be causing a p420, i use to have a p133 and p420..but when the ozone sensor was replaced i dont get that anymore..just the p420..i just want to make sure its a new catalytic converter i need b4 i have it replaced..thanks

My car has 182000 miles.
My car has an automatic transmission.

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.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car jumps while driving and has trouble going into gear.

If you have a manual transmission you may have an issue with your clutch. Automatic or manual transmissions can have electrical issues causing gear selection to be difficult. The jump you are referring to sounds like a hard shift. You...

Q: P0843

Trouble code P0843 pops up quite frequently on vehicles such as your Honda CR-V. The 2nd clutch transmission pressure switch is installed in the hydraulic pressure circuit to the 2nd clutch. The Powertrain Control Module (PCM) uses this information to...

Q: Car shaking after Check Engine light came on.

It sounds like you have a cylinder misfiring. I would recommend having a technician come out and check the code on the car to determine what is causing the misfire. It could be a wide range of things such as...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...