Is there a problem with replacing a non OEM catalytic converter in a 2003 cadillac. I've heard of computer issues if not replaced with oem parts

OEM Part Number(s): 19178928, 25161131, 25312197 replacements: (1A AUTO)1AEOS00163 or Walker WKEOS00092-02

Bank 1 Sensor 3 ,Sensor number #3 is downstream (after) the Catalytic Converter. There are also 2 upstream sensors Left or Front #1 and Right or Rear #2 upstream sensors.

Trouble Code: P0431

Warmup Catalyst Efficiency Low (Bank 2)
Possible Causes:


Air leaks at the exhaust manifold or in the exhaust pipes. Catalytic converter is damaged, contaminated or has failed Front HO2S or rear HO2S is contaminated with fuel or moisture. Front HO2S and/or the rear HO2S is loose in the mounting hole. Front HO2S older (aged) than the rear HO2S (HO2S is lazy).First check for leaks,if none found,maybe oxygen sensor is bad.Always use oem part,fits your connector,no splicing.Also check catalytic convertor..

Because the cat that is approved for California is "finer tuned" than the other 49 states. California emission standards are the toughest in the country, so many engine and emission parts are made just for those standards.

this obd2 trouble code table can help you understand the meaning of code.
and for p040,you can try:

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
for p0306, you can try
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

A 2003 vehicle probably did not need a new converter. Cat converters have to be run for years before they clog up. Depending on what kind of vehicle this is, you may have a post catalytic oxygen sensor problem. Also, depending on the vehicle, you can not just replace the converter with any old converter. Many vehicles require an OEM replacement converter in order for the sensors to work properly and these are expensive. Kansas City Converters (available online) sells replacement converters for a fraction of the price that will work with post catalytic sensors and not cause the check engine light to come on.

if they are "direct fit" there should be no guessing.......Have a muffler shop put the best quality converter on, you dont want the cheapest you can find. I would want the OEM converter.

P0420 indicates the computer thinks the catalytic converter isn't working as well as it should. This is determined by the PCM evaluating the switch rate of the front and rear o2 sensors. Once the rear o2 sensor switch rate reaches a point close to the front o2 sensor it sets the code. This can be a result of degenerated catalytic converter, or in some rare instances, bad o2 sensors. In most cases repairing this condition requires replacing the catalytic converter with an OEM unit. Aftermarket converters don't have the same quality and quantity of the precious metals that make up the substrate found inside. This usually results in the code setting again in just a few months.

P2179 System Too Lean Off Idle .Have read post where people have been getting this code after installing a aftermarket intake.

A p0420 code is set when the computer determines that the catalytic converter isn't doing it's job. In almost all instances that code can't set as a result of a bad o2 sensor so they probably didn't have to be replaced. The catalytic converter will need to be replaced, prefferably by an oem part. This can be pretty expensive and should be considered before purchasing the vehicle.

I have replaced a few bad converters on late model subarus in the past few years.

Essential it means the catalytic converter isn't working as it should. The only way to fix it is replacing the converter. I suggest replacing it with an oem part. I haven't had much luck with aftermarket converters, the code always returns in a few months. Oem converters can be a bit pricey because of the precious metals inside so prepare yourself for some sticker shock. The good thing is that it won't affect the drive ability of the car, so if need be you can live with it while you save.
Be sure to address any other codes you may have in the computer before replacing the converter as some may cause the converter to go bad again.