Q: I AM GETTING CHECK ENGINE LIGHT AND CODE P0420
MY CHECK ENGINE LIGHT CAME ON READING CODE P0420 COULD IT BE MY OXYGEN SENSOR DOWNSTREAM, OR BOTH SENSORS OR CATALYTIC CONVERTER SINCE MY MILEAGE IS HIGH 120000 MILES
My car has 120000 miles.
My car has an automatic transmission.
Hi Cornelius. Thanks for contacting us today. The P-0420 typically has to do with the catalytic converter in your vehicle, but can be triggered by damaged by O2 sensors, exhaust manifold or exhaust pipe leaks, or wiring harnesses that relay data to the ECU from these sensors. If all these sensors check out and there are no wiring issues or exhaust leaks, then the catalytic converter may need to be replaced. You might want to read this article on the P-0420 OBD-II code to learn more about possible repairs and diagnosis tips.
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
What others are asking
Advice on washing a car
It depends how dirty it gets. Now as for waxing your car (https://www.yourmechanic.com/article/4-essential-things-to-know-about-waxing-and-polishing-your-car)--it's a good idea to wax your car once every three months or sometime every season. So you might get it to a habit of, for example, waxing...
Shaking while braking
Hello. I’ve had experience with new rotors being warped right out of the box. There is a limited warranty on the rotors from the store. If you can return them and get new front rotors or get them turned, that...
Truck seems to hop at certain rpm
Hello. From what you describe, it would appear that your vehicle is experiencing performance issues, perhaps misfires under heavy loads. If the engine is misfiring under heavy load it will most definitely be felt through the transmission and chassis. This...
Coolant evaporating very quickly - 2001 Toyota Camry
Hello. If the coolant continues to go low, then there is a problem with the vehicle. It can be an external leak or the engine may have an internal failure which is causing the coolant to burn off. Since you...
Car shudders and hesitates when accelerating from a stop
This may be related to a few different things, such as low fuel pressure or a bad mass air flow sensor (https://www.yourmechanic.com/services/mass-airflow-sensor-replacement). Low fuel pressure may cause the car to shudder if it is starving for fuel when trying to...
Vacuum linse hooked up backwards on the engine.
Hi there. The vacuum hose to the valve cover is not to be under engine vacuum but rather under throttle vacuum. The lines on the valve cover are for ventilation only from leaking combustion gasses. The brakes will work very...
I had the blower motor replaced, it worked for the last week. Today the fans were kicking on and off then off completely.
This may be related to a faulty blower motor or blower motor relay. Occasionally, the blower motor itself will wear out or become faulty working intermittently as the brush contacts inside the motor wear out. The blower motor relay (https://www.yourmechanic.com/services/blower-motor-relay-replacement)...
99 GMC SUBURBAN running lean and starving for fuel when stompped on.
Hi there. Is there a check engine light on? If so, what are the codes, freeze frame data? Stored codes and data will aid in diagnosing what is occurring. What does the data look like from the O2 sensors? Which...
1/4 steel fuel line to 1/4 fuel pump quick connect, can't find -4an to 1/4 fitting ANYWHERE!
Hi there. If this is an OEM fitting application, your best bet is to contact a GM dealership, as they should have the correct parts you need. If it's aftermarket, having a place like Parker Hose or a local fuel...
Related articles
P0045 OBD-II Trouble Code: Turbo/Super Charger Boost Control Solenoid Circuit/Open
P0045 Trouble Code definition P0045 is the code for Turbo/Super Charger Boost Control Solenoid Circuit/Open What the P0045 code means This code...
Oldsmobile Certified Pre-Owned (CPO) Car Program
If If you are in the market for a used Oldsmobile vehicle, it may be that you have considered a Certified Pre-Owned, or CPO, vehicle. CPO programs allow owners of used cars to drive with confidence, knowing that their vehicle...
Understanding the Oldsmobile Oil Life System and Service Indicator Lights
Car symbols, or dashboard lights, are a car service reminder. The Oldsmobile Oil Life System indicates when and what service your car needs.
Browse other content
Maintenance
Estimates