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I have a 2001 Toyota Celica GT-S and recently my check engine light lid up. I took it to the shop few days ago and the technician hook up his device to my car and told me that it is probably my catalytic converter that is causing the problem. He told me that the part alone is really expensive. Hence, I told him to turn off the light for now and ill think about it. He also said that if it is really that problem (cat) the light will eventually light up again; so he advice me to just drive it around and see. He said that if the light comes back on and does not go away by itself, then it is probably the sensor(s) problem (which is cheaper to fix). But if the light just keeps going on and off (e.g. on for three days and off for three weeks), then it is probably the catalytic converter and I should replace it. Are all these information true? And if it is really my catalytic converter that is causing the problem, do I have to fix it? Will it cause greater damage(s) if I do not? how about safety issue? If I do have to fix it, can someone give me an estimate? The shop quotes me around $1,000 including a new catalytic converter + back sensor + labor and today, the light just pop back on again, what should i do? p.s. I am a girl that does not understand too much about cars, so I am sorry if I am asking a stupid question. Thank you

Answers from the Automotive Experts

Amanda J. Pierce, MBA Debbie, Normally a cat do not fail by itself, most likely some malfunction on your engine cause the CAT to fail. And this is if really your cat failed. This mean, if you get a code related to efficiency on cat below minimum, not always is bad CAT, can be the Oxygen sensors responding poorly. It is not recommended to install an aftermarket CAT, the CAT performance can be poor compared to the factory CATS, that after a year you could have a code related again, you can also contact local junkyards. You may come across a CAT from a 2001 Celica (or a like model, with same parts) with far less miles, and only have to pay labor charges to install. A Faulty O2 sensor (Oxygen) can sometimes cause the on-board diagnostics to assume you have a bad catalytic converter, when in fact you may not. These too may be able to be found in a junkyard to help narrow your problem.

Audra Fordin, Owner at Great Bear Auto Shop Hi Debbie! Happy New Year! First of all, what you are asking is NOT a stupid question. It is a valid, has a real answer and I work with this situation everyday so, you are not alone here. It is important to understand what these parts do, to understand why they are needed. The sensors your mechanic is referring to are (I am assuming) oxygen sensors. These sensors regulate the gas + oxygen mixtures your engine uses to make combustion (the fire) and burn gas efficiently. When the oxygen sensors (o2) are worn out,(which is not unusual, the approximate replacement for 02 sensor is aprox. 50k miles.) it effects your cars emissions (toxic gas released to the air we breathe). The catalytic converter (cat) is the "catalyst" that transforms the bad emissions into safer emissions, less harmful to our ozone layer, for us to breathe. After constant poor emissions going into the cat, the internal workings of the unit wear down, decreasing its ability to "clean" the emissions and it will need to be replaced. Now, to put it simply, for you and others who have the same great question, there is a cause and effect here. When the 02 is not working well (this will be shown to you when the engine light comes on), it wastes gas trying to make the right combo of gas + oxygen mix to make your car go. Thus, destroying the catalytic converter (very expensive). The bast way to eliminate this from happening... preventative maintenance! Replace your 02 sensors as per the manufacturers suggested mileage, OR when the indicator light comes on, address the situation and repair it quickly. Mechanically yours, Audra

Kristin Brocoff, Director of Corporate Communications at Hi Debbie, I know how frustrating expensive car repairs can be, but you should address the problem soon, before it causes serious damage to your vehicle. I do; however, recommend getting a second opinion before you pay for the new catalytic converter. CarMD offers a product that will tell you what the problem is and what repairs should fairly cost in your zip code. Every once in a while, a technician will get a diagnosis wrong, and you could find there's something smaller and less expensive that needs to be repaired. In my case, a couple years ago, my husband's car was diagnosed with catalytic converter failure. I used CarMD to confirm the repairs were necessary and the price we were being quoted by our dealership was fair. By having a second opinion (from a product or another mechanic), you'll feel better paying for those repairs knowing that they are necessary.

Laurie Sarno, Co-Owner at Super Girls Auto Hello Debbie-The check engine light is probably a catalyst efficiency code. Understand that only a very few "check engine" codes actually have anything to do with the actual operation of the vehicle. The vast majority are merely emission control warnings mandated by the government, and will cause no harm to the actual operation of the vehicle. Universal fit catalytic converters are sold at Autozone, O Reilly and Advance auto parts for anywhere between $75 and $100, and are not very difficult to install. The O2 sensors are available also for under $100. Unless the catalytic convertor actually melts down internally (rare) it will cause no damage to the vehicle. Should you elect to replace the catalytic converter, I would find a friend or acquaintance who can work on vehicles that will install it for you as it is not difficult. Hope this helps; Thanks Super Girls Auto.

Lori Johnson, Owner and Instructor at Ladies Start Your Engines Dear Debbie, First of all, catalytic converters rarely go bad. The reason they do is because unburned gas is dumping into them. This means that there is another problem further up in the engine. It sounds to me like this guy is guessing. Take it somewhere else for another diagnosis. You can go to places like Advance Auto and Auto Zone to get a free reading on your check engine light. Find out what the code is and then go to to find out what your code means. If you do have a problem with your catalytic converter the vehicle will most likely start to run sluggish and use a lot of gas. Eventually it will stall because the exhaust cannot escape out the tailpipe. Most important is to find out what made the converter go bad, if this is the issue. You may have a bad fuel injector or fuel problem in the engine. Good luck. Lori Johnson

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