Q: Check engine light won't shut off, problem in ECU

asked by on May 07, 2016

Firstly, thank you for guys so much! Okay, so my car has a check engine light that goes on and off randomly, but mostly on (side note: I don't know if this is relevant but when the check engine light is on, when I start the car and then let out the clutch, the rpms drop like it is going to stall for a second, then runs perfect. When it's not on the car starts very loudly and stays at 1,500 rpms like it should) The code the check engine light is giving is an error with the CAM shaft sensor, but, after replacing the sensor two times with two different mechanics (I made sure they got the sensor from the Hyundai factory) we ruled out it actually being a problem with that. Then my mechanic looked for wiring problems, and after a week of work, he decided it was a problem in the ECU. There is nothing wrong with my car other than the light being on and it doesn't effect my preformance at all, and a new ECU is $1,100 to replace. I was wondering if there is a less expensive way to fix this? Thx!

My car has 106000 miles.
My car has a manual transmission.

You’re very welcome.

If you’re getting a code for the cam sensor, this doesn’t always mean the sensor is the problem. You may have a problem with slack in the timing chain or belt causing the crankshaft and camshaft sensors to not be in sync with each other. This would account for the engine to idle low and then jump up. If indeed the ECU has failed, there is unfortunately no way around it, and it just needs to be replaced. You could try checking with the dealer to see if there is a software update available for the ECU that could solve this issue. The best solution at this time would be to have a qualified technician, such as one from YourMechanic, come out and start the car cold and see if the engine timing chain is making noise at that time, and perform any additional diagnosis for this problem.

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