I have a 2003 Toyota Corolla S, sedan, with 120,000 m. My check engine light went on. The dealership says I need a new catalytic converter ($1500 with labor). They say that if I don’t replace it, the car could just stop operating (“press on the gas, and there’ll be no response”) – and I’ll be polluting. An independent mechanic says there’s no hurry – I can safely ignore the light unless new problems crop up. He says that with regular maintenance and checks, it will be clear when the converter really needs to be changed, and that he can hook the car up to the computer regularly to see if the check engine light has any other reason to be on. What should I do? PS. I bought the car used a couple weeks ago. There is a rattle and a low idle. I’ve been told I need a transmission flush, throttle body cleaning, and some basic maintenance. The dealer also said I need a new serpentine drive belt tensioner, but the independent mechanic says it looks fine. Both agree there are no cracks on the belt.
There is no code for “bad catalytic converter.” There are codes that could indicate that is the problem, but there could also be other problems such as bad sensors.
It is unlikely that the car will stop dead if you don’t replace the cat. You may be polluting more than you should, and you will fail an emissions test if your state has one.
Your independent mechanic seems like a helpful guy, offering to check for codes once in a while enables you to be a cheapskate on an old car. Some mechanics wouldn’t want a customer like you. What would he charge for a new cat? $1500 is pretty high even for a dealer.
Transmission fluid change is needed on a car of this age if it was never done. It’s usually better to simply drop the pan and let the oil drain out. Power flushing can stir up debris that has settled and force it into places you don’t want it to go.
How about taking your car to a local autoparts store and have them read the code and tell you what it is. Not what they think it means, but the actual code. It should be in the format [P1234]. Post the results as a response to this or your original message. Then maybe we can determine why the light came on. Ignoring the CEL (Check Engine Light) is not a good idea. Since you only have one light, you will not notice if a second problem develops. BWT that rattle sound is an indication that the converter maybe going or gone.
You may need a new converter, but you can get a good one for a lot less than the dealer will charge if one is needed.
[i] I've been told I need a transmission flush, throttle body cleaning, and some basic maintenance.[/i] Transmission flushes are usually a profit device. I would much rather see a transmission fluid change with the filter cleaned. If that was the timing belt they were talking about then we need to know if you are still on the original belt. If it is an original timing belt, you are on borrowed time and if it goes it is mighty expensive.. If it was, how long since the last change. At 120,000 miles you are past due. Take a long look at the owner's manual. Look up maintenance items. Make sure they are all up to date. Not doing maintenance is the most expensive way of owning a car I know of.
The problem with ignoring the CEL is that if something else serious happens that needs addressing you’ll never know…your early warning system, your CEL, will have been made ineffective.
The code simply says that based on the ECU’s comparison of the signals from the upstream xoygen sensor and the downstream oxygen sensor, your cat converter is not operating efficiently. The only way to find out if it’s actually the converter or the sensors is to actually put the sensor readings on a scope together and look at the. That way the tech can see if the sensors appear to be putting out appropriate signals. Your shop should be able to do this.
I’d have the independent read the fault codes from the ECU, diagnose the known code(s), give it a good going-over and make a list of everything that needs doing. The rattle may or may not be a sign of something serious, but you need to know. He should be able to tell you.