Trouble Code P0430

[Doug Duncan]

My GF’s Father has a 2001 Nissan Sentra 1.8L with real low miles and Service Engine Soon light came on and after a bit started flashing while vehicle was staggering at idle, low speeds and running rough at speed. Scanner at Auto Zone threw a code stating Cylinder 2 Misfire. With that we flipped the Ignition Coil from cylinder 2 to 1 and vehicle threw a Random Misfire Code which told us the Ignition Coil was bad. New Coil car starts and runs fine engine miss is gone so we cleared the code. Next Day, Service Engine Soon Light goes on but no significant performance issues. Scanner throws a P0430 Code “Catalyst Below Threshold; Bank 2” Guy tells me O2 Sensor Downstream from the Cat is bad. Or Catalytic Convertor is bad. I do not believe the Cat is Bad because at highway speed if you stab it it hits passing gear and accelerates steadily with zero hesitation, I am thinking Evaporators System Leak somewhere. Question: Am I on the right track? And would a Starter Fluid Test be appropriate before swapping O2’s and Cats? Additional information, car has 27,000 original miles on it and was previously owned from a 92 year old lady who couldn’t drive it much the last year and it sat quite a bit un-started, undriven. The day after we replaced the Ignition Coil I ran some Fuel Injector Cleaner by adding it to the tank and filling it up. I am thinking long term sitting without running engine winters/summer on east coast may have weekend vacuum lines, Air Filter Housing and the like and will perform in depth visual inspection prior to any of your recommendations. Please Help!

Topic

[Richard Kirshy]

First, a EVAP leak would throw a different code set P0455, P0456 etc

P0430 NISSAN Possible Causes:
Faulty Three-way Catalyst Converter
Exhaust Tube
Intake Air Leaks
Faulty Oxygen (O2) Sensor
Faulty Fuel injector(s)
Leaking Fuel Injector(s)
Faulty Spark plugs
Improper Ignition Timing
Faulty Engine Control Module (ECM)
Dirty Air Filter

Considering the age / mileage of the vehicle …
An extremely low mileage vehicle can develop issues from not being stored properly for long terms.
Wouldn’t be surprising to hear most if not all hoses, belts, rubber components will require replacing quite soon.
Along with possible brake system and cooling system problems.
Also keep an eye on gaskets.

[Jeffrey Voight]

Just because there is no restrictions at the catylitic converter doesn’t mean the converter is good. The code is reporting that the converter isn’t doing it’s job and it’s not eliminating raw gasses. As stated above, that doesn’t necessarily mean the converter is bad, but it was running more raw fuel through it due to the misfire. The misfire along with the current code indicates that the converter was damaged by the misfire. That being said, just because that is the most likely fault doesn’t mean that you go ahead and change the converter. You should check all of the conditions listed by @Richard Kirshey first. You can use a thermal gun and record the temperature in front and back of the converter. It should be hotter in the rear. Using a scanner to read the downstream O2 sensor activity would be a great way to diagnose this also. But the converter is the first suspect.

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