Q: Have a 2006 Lexus IS350 with a code of P0420 saying catalyst System Efficiency Below Threshold Bank 1

asked by on

Car is jerking and have code P0420 Catalyst System Efficiency Below Threshold (Bank 1) What is this

My car has 150000 miles.
My car has an automatic transmission.

Hi Phoebe. Thanks for contacting us today. When the oxygen sensors have readings that are similar to each other, it is an indication that the catalytic converter is not working as intended. If the voltage of the downstream oxygen sensor decreases and begins to fluctuate like the upstream oxygen sensor, it means that the oxygen levels are too high and the Powertrain Control Module (PCM) will store the P0420 trouble code. This can cause poor fuel mileage, shaking and vibrating (as you’ve described) and poor engine efficiency. Since the O2 sensors or the catalytic converter itself could be the source of this problem, having the root issue correctly diagnosed by a professional mechanic is the best initial step.

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
  1. Home
  2. Questions
  3. Have a 2006 Lexus IS350 with a code of P0420 saying catalyst System Efficiency Below Threshold Bank 1

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: My 06 Cadillac CTS display on the boad says 'Service anti-theft system'. Is this something I need to take to a mechanic to check

Hello, thank you for writing in. The first thing you want to do is scan the vehicle for diagnostic codes. These will tell you what about the anti-theft system is causing issues. From there you will have to decide if...

Q: My brakes hiss back at me

That hiss you hear is a vacuum leak. That leads to the hard brake pedal. Power brakes rely on vacuum to make braking easier. The vacuum leak has reduced vacuum within the brake booster and is making the brake pedal...

Q: Humming/vacuum sound from engine

Based on your description, it sounds like you might have a vacuum leak. I would recommend looking around under your hood to see if any hoses are flat, torn, or have holes in them. This will create a vacuum leak...

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 Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...