2001 Hyundai Sonata Check Engine Light On Transmission Shifts Hard
Reader Question: I have a 2001 Hyundai Sonata with 152,000. I have had regular maintenance done on it at every 15,000/30,000/45,000, etc. miles.
Currently when I drive it when it shifts (automatic transmission V6) around the 25MPH point it shifts rather hard unless when just above 25 MPH I let up off the gas to allow easier shift.
When it does make the hard shift, the Check Engine Light will come on and the car seems like it is driving in the wrong gear (I guess) but it will drive.
A friend put the hand held computer on it and the code shows I need a speed sensor. Is that enough or do you think I am looking at transmission problems? Is there a code when it is the transmission?
Thank you for your advise.
Jeannie
Hey Jeannie,
I really need a little more information and would like to run some tests myself to really be sure what is happening here but if you have a speed sensor code that is showing up in the computer memory, I would look into that code more and test the sensor.
This could very well be a bad speed sensor problem or there could be something wrong internally with the transmission. You do have many miles on this vehicle, so internal transmission wear would not surprise me at this mileage point.
Before you do anymore than replace the speed sensor, I would get a reputable transmission shop or even the Hyundai dealership to diagnose this problem further. Your regular mechanic is probably not the best guy to troubleshoot an electronic automatic transmission problem.
If the transmission is deemed to be the culprit, get 3 estimates from local transmission shops for a complete overhaul. You might not need a complete overhaul for this problem but at this mileage, I would be prepared to overhaul it once they disassemble it and do some inspections.
You do not want to be sticker shocked if they later determine an overhaul is needed.
Blessings,
Austin Davis
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Filed under: Check Engine Lights
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Sounds like the transmission is slipping or the fluid could be low.
I have a 2000 Sonata GLS V6 as well, and mine does something very similar, it will abruptly shift when cruising, from 4th to 3rd or vise versa, i mean ABRUPTLY. When it does this the check engine light comes on and it throws 3 codes u3900, p0705 and p0715, the first code is unknown, the second transmission range sensor and the third is the speed sensor, peculiar huh….
Br,
Daniel
I am not a “transmission mechanic” but I would suspect an internal transmission issue causing this problem. This could be an expensive transmission to overhaul so I highly suggest you get 3 quotes AND 3 separate diagnosis before you jump in and overhaul this transmission.
This is interesting, I have an 02 Sonata that shifts like this. We call it a “bunny hop” and we sit in anticipation of it when we’re driving…it can really jolt you at times.
My check engine light is now on and despite being re-set it came right back on, I just paid for my tags but can’t pick them up until I pass the smog test but I can’t have my car smog tested with the light on, it’s illegal here! We had it DX’d and they said it was the speed input/output sensor so we had it replaced, light is still on. The mechanic told us it’s our transmission and that it needs replacing. We’re going back and forth with what to do, this car’s been nothing but a money pit for us and it’s got under 80K on it so it hasn’t been heavily driven over the years.
I would suggest you see the dealership and let them diagnose the problem for you, you can always have another cheaper mechanic perform the repair once you know exactly what the problem is. This could be something as simple as a bad spark plug wire causing an engine missfire.
I have had the same problem with our car (2001 Sonata 4cyl) and have been told repeatedly (at least 10 times) that “we can’t find any problem”. I have brought my car to the dealer since 40k miles with this problem. NOW that my warranty is gone they all of a sudden find that my trans is shot and refuse to fix it. I have a lawsuit pending with my local dealer. Oh..and my car only has 70k miles on it at this point. This is a known problem…they just stall you until your warranty is gone.
Please keep us posted as to the outcome, it will definitely help the next person.