Skip the auto shop - Our mechanics make house calls

Q: Scan vehicle Code P0430 Cataylic system efficiency below threshold bank 2

asked by on

Hi,

Month ago had a misfire on my vehicle Lincoln Town Car so I use a scanner and had a code which said cyclinder 2 misfire so I took it to my Mechainc and he replace just 1 coil and 1 spark plug the rest was not replace my Mechainc said you don't need to replace them til it fails. Car ran nicely after a month now my car as another problem check engine light on and blinking as well my car is running rough, jerking, and shaking when I acceralte. So I went and bought a bottle of Fuel & Exhaust system cleaner which is suppose to clean the Cataylic and 02 sensor to give a shot to see but no luck but it did help a little bit so I ran the scanner and it give me a code which say PO430 Cataylic system efficiency below threshold bank 2. Can you please tell me what is the cause of this problem is it the 02 sensor or Cataylic convertor or something else as I have no clue?

My car has 214500 miles.
My car has an automatic transmission.

The code is meant to indicate your catalytic converter is not performing up to par with the EPA (environmental protection agency) standards. Your car uses the oxygen sensors to monitor the catalytic converter (cat) efficiency. There is an O2 sensor before and after the cat. If the catalytic is working effectively, the O2 sensor after the catalyst will show much less HC’s (hydrocarbons) that at the front of the cat. If the cat is not performing as it should, the rear O2 will see close to the same amount of HC’s after the catalytic converter.

Most of the time this code requires the replacement of the catalytic converter. There are times when one or both of the O2 sensors that monitor the cat are bad. This can be determined by monitoring scan tool data for a reaction from the O2 when you snap the throttle. In addition, you can use an exhaust gas analyzer monitor the tail pipe emissions from a cold start up. The cat takes sometime to begin working on a cold start, so there should be a significant difference in tailpipe emissions once the cat warms up. Gas analyzers are very expensive, so it is unlikely most people will have access to one. If you need a definitive diagnosis, a certified professional from YourMechanic can come to your car’s location to pinpoint the cause of the code and proceed with repair.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
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. Scan vehicle Code P0430 Cataylic system efficiency below threshold bank 2

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: Can my 1999 town car use 89 octane even though it says 91

If your vehicle says premium fuel only on the gas gauge then you should use only the premium fuel. In a pinch you can run the 89 octane fuel and try not to do any heavy acceleration to avoid engine...

Q: Acceleration issue, RPMs increase but not speed

If your car is revving up but not moving, or is slow at gaining speed, then you have a slipping clutch. If you have a manual or automatic transmission it will still be a clutch issue. A mechanic with experience...

Q: Rear brake cylinder leaking

You will need to have the brake cylinder replaced. I recommend replacing both sides so that brake pressures will be equal. Once replaced, its a good idea to flush the brake system with fresh brake fluid. I suggest having a...

Related articles

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...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...