Q: Check Engine Light is on - trouble code P0420

asked by on

I have changed the catalic converter changed the oxygen sensors front and back changed the coolent sensor but the light came back up again can u help plz Amar

My car has 152000 miles.
My car has an automatic transmission.

As you may know, trouble code P0420 relates to the inefficiency of the catalyst system, which detects the presence of oxygen in the exhaust gases. This can be caused by failing O2 sensors that need to be replaced. This can also happen when the fuel supply is incorrect, supplying too much or too little fuel to the motor which results in the O2 sensors reading too much or too little fuel present in the exhaust gases.

This may happen when the fuel injectors are leaking or working intermittently due to incorrect pulses, an intake air leak, incorrect ignition timing, or even bad spark plugs. I would recommend having an expert, such as one from YourMechanic, come to your location to determine why exactly the Check Engine Light is on and why it is throwing this code.

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. Check Engine Light is on - trouble code P0420

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 2003 Camry is making a noise when turning.

Hi There, A number of things may cause the vehicle to make this kind of sound when turning the wheel. Things like worn out ball joints, damaged tie rod ends or potentially a damaged power steering rack. I would suggest...

Q: Diagnosed as code P0420

When you get a P0420 code that indicates a failing catalytic converter. Most of the time that is exactly what it is. In some cases, it can also be caused by a bad oxygen sensor. I typically use a computer...

Q: Transmission over temp

The shifting problem you are having may be a sign of low transmission fluid or a faulty transmission control solenoid. As you know, automatic transmissions use pressurized hydraulic fluid to change gears. Every time a gear change is required, the...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.