The orange check engine light is a car's way of ... a bad O2 sensor can damage components like the spark plugs and the catalytic converter. The first thing you should do is to pull over and check whether anything is wrong with your engine components. if it doesn’t, it may be time to ask your mechanic to check it out. It converts carbon monoxide and other harmful gases into less harmful byproducts. It stayed on for a while, went off, came back on, went off, came back on. A flashing check engine light means that you need to pull over immediately as your vehicle has a serious issue that could cause severe engine damage. It didn’t make sense since the car was running fine. So, if your converter is marginal, and you did a lot of stop-and-go driving, which creates high demand for the converter, that may have turned on the check engine light. "Check Engine Light" Codes P0420 and P0430 Replacing a catalytic converter or "cat" has become a big, expensive drain on a lot of people's budgets these days. Recently at 269,000 miles the P0420 code came on again. I don't know why or how it works; but it worked. The check engine light is for mostly minor issues. We get it turned off periodically, and then it goes right back on. I have a 2001 grand prix GT that was having acceleration issue and I determined that it was a catalytic converter issue. The check engine light only comes on in certain conditions: If the check engine light is coming on intermittently, be sure to notice any changes in the performance of your vehicle when the light is on.If you do notice a difference, try driving your vehicle as little as possible until you can bring it in for service. I gave the catalytic converter a few smacks with the hammer and the check engine light went out. Toyota was kind enough to do a "good will" no charge warranty replacement. That will be a $1600 bill. Even after tightening, it will take some time for the light to go off. When the light pops on, your car’s engine control module (ECM) will also store a diagnostic trouble code (often a P0420 code) in its memory. In most cases, your Toyota Corolla light will go off after about 20-40 miles. In most cases you will receive a P0420 or P0421 code. Gas cap issues can reduce fuel pressure and allow fuel vapors to escape, reducing fuel economy and increasing harmful emissions. It runs great, except that there seems to be a problem with the catalytic converter, causing the orange "check engine" light to remain perpetually on. I did the "dance" and only saw "P 1684" "-----" and "donE". I checked the gas cap and waited a few "driving cycles" before calling the dealer. If the catalytic converter is replaced without repairing the misfire, the new catalytic converter will go bad again. The question of whether the check engine light will reset itself is often asked by many drivers. Loose Gas Cap: Your gas cap is loose, broken, or simply missing. I had them change my sensor, drove 10 miles and my check engine light came back on, so I figured it was the catalytic converter. The service engine soon light never came on. To make things worse, I wouldn’t pass emissions inspection with the check engine light on. The car runs fine, so signs so far of misfire or bad fuel consumption. We recommend you try tightening it first and then see if the light goes off. A misfire will turn on your check engine light for sure, and severe misfires will set your Check Engine light blinking. My check engine light came on about a week ago. That can include a minor misfire or a loss of pressure in the fuel system, among many other possibilities. All that code says is either Converter operating below efficency or Converter operating below threshold. 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