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Q: Speedometer not working

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I have two codes popping up from the engine light. P0720 and P1529. Is this a serious problem or is it just the speedometer? I think I just need a speed sensor replacement but I would like to make sure. I stopped driving it in fear of more damage. When I try to accelerate, it gave me a thud after slowing down and it doesn't make a sound when I stop at a stop light. It takes a long time to move and speed up.

My car has 206000 miles.
My car has an automatic transmission.

Hello there, you are correct. Both of the codes on your 2001 Hyundai Elantra can relate to the speedometer. The P0720 code is for output speed sensor circuit fault, this can be caused by a faulty speed sensor, a wiring harness fault, or a failing speedometer. The P1529 code is more general and refers to a transmission control module fault present. Your vehicle will still need to be diagnosed to properly determine what the root cause is. A qualified technician, such as one from YourMechanic, will be able to inspect the Check Engine Light so that you can proceed with the proper repairs.

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