When I failed DEQ it said these things:
1.P0325 Knock/Combustion /Vibration /sensor 1 Circuit - Bank 1 or Single Sensor
2. P0420 Catalyst System Efficiencey Below Threshold - Bank 1
3. P0139 O2 Sensor Circuit Slow Response - Bank 1 Sensor 2
4. P0455 EVAP Suystem Leak Detected (large leak)
5. P0457 EVAP Suystem Leak Detected (fuel cap loose/off)

So my neighbor reset all my codes and made me drive the car for a week.
Now it shows the following: (his system is not quite as sophisticated as the DEQs but here it is)

1. Knock Sensor Bank 1
2. P0420 Code (catalytic convertor)

then he told me to drive it for awhile longer and see if the Oxygen sensor code comes back.

So I guess I am looking for a second opinion: (based on the little bit of information I have so far)

What parts do you think I need?

My neighbor can fix it but I don't want to buy a new catalytic convertor unless I need to.

 

How long has the check engine light been on? Do you notice any performance issues with your car? How many miles are on it, and do you keep up with maintenance items?

You really need to diagnose the problem before throwing parts at the car.

If your neighbor's scanner can read live data or read freeze-frame (the parameters when the code is set), then you may be able to figure out the root cause. Look at fuel trims and ignition timing to see if the knock sensor is causing the engine computer to advance the timing. Also, see if the scanner can pick up any misfires for each cylinder.

Are you getting a knock code along with the O2 sensor code because the converter is toast, or do you have a knock sensor problem (or engine knock) and it messed up your converter.

If this were my car, I'd probably remove the catalytic converter to see if the honeycomb of catalyst looks normal or is damaged. If damaged, then you will have to replace, but you may have an issue upstream causing the converter damage.

 

It has approximately 260K miles on it. I change the oil. it probably could use a tune up. I gave it one about a year and a half ago. And it does not seem to have the same power it did a year and a half ago.
I do not hear any engine Knock.

Thank you for advising me.

 

What was the mileage when you gave it that tune-up?
- how many miles are on the spark plugs?
- how many miles are on the air filter?

 

It is probably time for a tune up. It has to have been 18 months at least since it was tuned up. I started a new job about 18 months ago and it has not had one since then and probably much longer than that.
The only thing I do with any consistency is oil changes. That gets changed every regularly. I don't go for 15,000 miles like the oil says but I change it out around 3 or 4 thousand with synthetic and a new filter

is a tune up on this vehicle just plugs, wires and pvc valve?

 

Spark plugs.
IIRC this has a coil on top of each spark plug, so there are no plug wires.

Air filter? I've seen them go a long ways but YMMV for how dusty your area is.

PCV valve is not a regular tune-up thing. It's not the cheap little plastic valve like older Honda. But at 260k miles maybe...