Q: Check Engine Light on on 2007 Toyota Corolla

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The check engine light came on my Toyota Corrola 2007, took it to the dealership for repair. I was told they need to replace the ignition coil (for code PO353), i took the car back since they told me "everything is all set, we fixed the problem". The following day i took it to work, lo & behold the light came on again. I took it back & til now they couldnt tell me what's wrong w/ my car.
(1) Answer
I don't have experience with this specific vehicle or this code, but I have dealt with many similar issues and identifying the problem can be very difficult. If the problem occurs intermittently, then replacing the coil was a good first step.
Have you experienced any issues with the engine running poorly?
I would ask them what they have done to try and determine the cause, these are some things they should have done.
Checked the wiring and terminals between the coil and the control module. The terminals must all be checked for the correct tension and replaced if not within specification.
They should have checked all of the technical information from Toyota about this problem.
Hope this helps, let me know if you need any more info or clarification on anything.