Service Engine Soon Light On In ’02 Lancer Catalytic Converter

Question: Service Engine Soon Light On In ’02 Lancer Catalytic Converter,
I just stopped at autozone, got my computer read via the scan tool, and was told I need a new catalytic converter. However, the guy who read me the codes said some cars have more than one converter. Here is exactly what is on the print out:

Code: P0421 OEM Brand: OBDII
The PCM has determined that the warm up catalyst efficiency for bank 1 is below threshold for the current engine operating conditions. (Bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank.)

Code: P0421
OEM Brand: Domestic

Catalyst efficiency low bank 1
Explanation: The oxygen sensors monitor the catalytic converters ability to store oxygen.
Probable Causes:
1- Catalytic Converter defective (Failure possibly due to #2, 3, or 4.)
2- Engine misfire or running condition.
3- Large vacuum leak.
4- Engine oil leakage into exhaust-valve guide seals, piston rings.

How do I tell whether or not I actually need a new converter, and whether or not I have more than 1? My car is not shaking or revving up/down when I’m idling or kicking in and out of overdrive while driving. I do not smell burning oil or gas. I have already replaced the oxygen sensor in front of the catalytic converter. There are no leaks, as far as I can tell from looking under the car after letting it sit for a while. The only problem I’m really having is that before my engine light came on, I was getting about 400 miles to a tank. Now, I get normal gas mileage for the first half of the tank, and it drops to about 120-150 miles for the last half.

The man also suggested I take my car to meineke, as they can check to see whether or not it is the catalytic converter, but I’m sure I’ll be charged. Does anyone know of a better way to tell or should I just find a place that will test it? What major chain stores have you had the most success with buying parts/having them installed, etc?

Also, I already looked up the specs for my car but no info on the cat. (I have a 2002 Mitsubishi Lancer OZ Rally, SOHC if anyone is interested in double checking.)


Best answer for Service Engine Soon Light On In ’02 Lancer Catalytic Converter

Def sounds like a converter problem, I would go have it checked and im sure you will find it needs to be replaced. The converter being blocked can cause your mpg to drop drastically if it is blocked. Your best bet would be to have it replaced and unfortunately they usually are not cheap to replace.

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  1. Rockrib2000
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