I can not get much power to go over inclines very well and there is a PO420 error message in its computer.I've been told it's a catalytic converter problem but there are 3 on the exhaust sytem(2 in front and one in rear).Any way to find out which one?

The PO420 code is a generic code indicating a problem with the catalytic converter system efficiency below threshold. This issue can be caused by several factors, including:

1. A clogged or failing catalytic converter
2. An exhaust leak before the catalytic converter
3. A malfunctioning oxygen sensor
4. Fuel system issues, such as a clogged fuel injector
5. Engine misfire
6. A damaged or failing ignition system
7. A vacuum leak

Here are the steps you can take to diagnose and fix the issue:

1. Check the catalytic converter: If the converter is clogged, it may need to be replaced.
2. Examine the exhaust system for leaks: Leaks before the catalytic converter can reduce its efficiency. If a leak is found, it should be repaired.
3. Replace the oxygen sensor: If the oxygen sensor is malfunctioning, it can cause the engine to run too rich or too lean, which can affect the catalytic converter.
4. Check the fuel system: Clogged fuel injectors can cause a lean fuel mixture, which can harm the catalytic converter. Have the fuel system checked and cleaned as necessary.
5. Repair any engine misfires: An engine misfire can damage the catalytic converter over time. Fix the misfire and see if the code returns.
6. Check the ignition system: A faulty ignition system can cause a misfire and damage the catalytic converter. Have the ignition system checked and repaired as needed.
7. Find and fix any vacuum leaks: Vacuum leaks can cause a lean fuel mixture and damage the catalytic converter.

It's best to have a mechanic diagnose the problem and perform the necessary repairs, as some of these repairs can be complicated and require specialized tools.

P0420 Catalyst System Efficiency Below Threshold
from the misfire raw fuel damaged the catalytic convert .
P0300 random misfire . Without testing we'd be guessing ! Fuel system testing , ignition system testing , engine management system testing , back pressure test the exhaust .plugged catalytic converter

Pesky PO420 Codes - Eastern Catalytic

www.easterncatalytic.com/education/tech-tips/pesky-p0420-codes/

One of the most annoying is the persistent PO420 diagnostic code (Catalyst System ... not only shows its teeth when the catalytic converter is on the blink, but can also be ... Most, if not all, catalytic converter failures are caused by a problem or ...

P0420 Error Code: Catalyst System Efficiency Below ...

www.obd-codes.com/p0420

Repair information for the OBD-II trouble code P0420 - Catalyst System Efficiency ... If they have failed, it is likely due to something else that caused it to fail. ... the catalytic converter is broken or failed, it may be restricting the exhaust which will ...

explaining trouble codes po420 - po421 - Discount Catalytic ...

The after market cat is the likely problem. Catalytic converters are not all the same and over time our shop has learned which aftermarket ones will work and which ones will not.

The computer is looking at the downstream O2 sensor (the one after the cat) to determine cat efficiency. If the downstream O2 sensor is switching simular to the upstream O2 sensor (the one before the cat) than the computer interprets this as a bad cat. The rear O2 sensor should hold a steady voltage at idle once the car is warmed up.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Catalyst System Efficiency Below Threshold (Bank 1)

A code PO420 may mean that one or more of the following has happened:

• Leaded fuel was used where unleaded was called for
• An oxygen sensor is not reading (functioning) properly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
• Retarded spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of reading

• Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
• Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
• Inspect the downstream heated oxygen sensor (HO2), replace if necessary
• Replace the catalytic converter

P0420 = catalyst system efficiency below threshold (bank 1)

the computer is detecting that the O2 sensor downstream of the catalytic converter on the bank of cylinders that includes cylinder 1 is starting to mirror the same cross counts as the upstream O2 sensor. This usually means that the catalytic converter is worn out and must be replaced. However, the oxygen sensors must check good---a bad or "lazy" oxygen sensor won't give an accurate picture of catalytic efficiency.

PO420 code is for catalyst system efficiency below threshold (bank 1) Usually it means that it is time for a new catalytic converter on bank number 1. Cylinder bank number 1 is always the bank with the number 1 spark plug in it.

The PO420 means that the Catalyst System has an Issue'

The actual error is

"Catalyst system below Threshold (bank 1)"

As mentioned above, the code's description is Catalyst System Efficiency Below Threshold (Bank 1). OK, now tell me that again in plain English please.... let's break it down: the catalyst system being referred to is your three-way catalytic converter; so the catalytic converter is not working properly (i.e. it's not efficient). Bank 1 refers to the side of the engine which contains cylinder #1. On inline engines such as 4 & 5 cylinder engines, there is only one bank. So, to really simply things let's just say that the efficiency of the catalytic converter and/or exhaust pipe and/or O2 sensor is not so great.

There are a number of things that could be causing this p0420 catalyst efficiency code. The most common thing is the catalytic converter itself is no longer functioning properly. The other likely thing is the rear O2 (oxygen) sensor is no longer working properly. Other things could include exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc.

You can search for the Information on the web. Just type in the actual error above into you fav search engine!

Hope that helps...

CODE PO420 CATALTYLIC CONVERTER SYSTEM FAULT.ITS SAYING FAULTY CATALTYLIC CONVERTER.IF IT BEEN A WHILE IF YOUR CAR HAS A WHOLE LOT OF MILES ON IT.YOUR SPARK PLUG CHANGE IS DUE AT 120000 MILES. DUE A LITTLE TUNE UP CHANGE AIR FILTER AND FUEL FILTER.SEE IF YOU HAVE ANY ENGINE FAULTS BAD PLUGS DIRTY INJECTORS ANY THING UP SET FUEL SYSTEM CAUSE CAR TO RUN RICH.EXCESSIVE UNBURN FUEL WILL GATHER IN CATALYTIC CONVERTER CAUSE IT TO BURN OUT.SHORTING LIFE OF THE CATALYTIC CONVERTER.

Not just a faulty catalytic converter will trigger this code. Many other issues can trigger this code.

• Leaded fuel was used where unleaded was called for
• An oxygen sensor is not reading (functioning) properly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
• Delayed spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings

Possible solutions:

• Check for exhaust leaks at the manifold, pipes, catalytic converter.
• Replace Coolant Temperature Sensor
  
• Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
• Inspect the downstream heated oxygen sensor (HO2)
• Replace the catalytic converter
• Have timing adjusted