Check engine light after dealership oil change

I recently had an oil change on my 2000 Corolla (~84k miles) done at a Toyota dealership. Within a couple of miles after leaving the dealership, the check engine light came on. I went straight back to the dealership, and was told that the problem was the catalytic converter.

The car has an aftermarket catalytic converter since ~70k miles (about a year ago), when I hit a trailer hitch on the freeway. The check engine light came on back then (the cat had been ruptured), but has never been on since.

Now the guys at the dealership tell me that aftermarket catalytic converters just don’t last more than 10-15k miles, and that the check engine light came on within minutes after the oil change purely by coincidence. They also tell me that the only way for my car to pass state inspection is to have the cat replaced.

Even though I do accept the theoretical possibility of such coincidence, the two events (dealership visit and check engine light) are, in my mind, more likely than not to be correlated.

My question is: is there something the dealership could have done, intentionally or not, to trigger the catalytic converter code? Any thoughts?

Many thanks,


So,are we to assume the dealership did pull the OBD codes, and they indicated the catalytic converter? The “Check Engine” light in and of itself can mean many things. Need more information…


Benaman is correct. More analysis needs to be done than just pull a code and jump to a hard conclusion. For example a cylinder may be misfiring. The engine may be burning oil. You need to find the root cause of the code. Did they reset it? if so did it come right back on or did it stay off for a while. Did you change the type of gas you normally use. Did the dealer use the correct grade of oil? You need to have someone look at it methotically. You may very well need a new cat. But find out why this one died so early and fix the root cause or else you may be repeating this again shortly. Also I would look into the warrantee on the replacement cat. Good Luck

First, unless the dealer recognizes the brand of aftermarket cat you have, and they know from experience that this particular brand is short-lived, then the blanket statement that all aftermarket cats last only 10-15k miles is simply not true.

If we assume that there was no mistake with the code, and the OBD II system is generating a code for catalytic converter, then I would bet that the timing of the Check Engine light was a coincidence. There are a number of things that could happen during an oil change that might cause a Check Engine light, but it seems unlikely that something could happen that would cause a catalyst code. Is there a way that you can run the car up on ramps (or a curb) and take a good look at the bottom to check for damage caused by the hoist?

Listen carefully to the car, does it sound like there might be an exhaust leak anywhere between the catalytic converter and the engine? Put you hand near the joints in the pipe to try to feel any leaks.

Another thing that can cause a catalyst code on an OBD II system is an oxygen sensor that is getting old and slow to respond. That is hard to diagnose, because the usual oxygen sensor tests won’t detect it. Only an oscilloscope will detect it. However, 84k miles is pretty young for an oxygen sensor to get sluggish.

Dealership 99% likely did nothing. In the 1% case they did it was not intentional.

The aftermarket cat answer is likely a response to work they perform replacing aftermarket garbage with OEM quality. A blanket statement stating all aftermarket only lasts 10-15k is simply not true. Quality varies aftermarket from junk to get your someone’s heap running that last 6-12 months all the way to surpassing OEM quality. They cannot look and say.

This needs to be looked at further.

The dealership did pull the OBD codes, and they indicated the cat. They did a reset, and the check engine light stayed off for a while (~50 miles). There is no visible smoke coming from the tailpipe, no change of gas type (same station, same grade), and judging from the sticker they put on my windshield the correct grade of oil was used. It is true that I should have someone look at it methodically. Many thanks for your answers.