I just bought (used) a 2001 Sonata GLS The check engine light came on and I cleared it by removing the Neg batt cable for a short time. A few days later while slowing down to stop the transmissiion made a slight "thump" sound as it was down shifting. The check engine light came back on..........I went to AutoZone and had them check the trouble codes: They found these two codes: P0715 and P1529. I've looked them up on the internet and found them to mean: Input/Turbine Speed Sensor Circuit Malfunction. and: SCAIR Solenoid Circuit Malfunction. BUT, What do they mean??? Where do I start to correct this issue. Any suggestions will be most appreciated.

Best & cheapest is, to have a Hyundai tech check the input speed sensor connector, and have him check in the TCM for more codes. P1529 referees to the fact, that there may be more codes in the TCM.

Had a similar problem.

Check on the spark plugs cable. There is a possibility of a burnt through on the insulation of the cables.

Get the 4 cables replaced and it should be fine....

????????????? what has this got to do with the input speed sensor ???????????????

I talked with a Hyundai tech over the phone and he suggested getting a AT flush and then replacing both the input and output speed sensors....... WOW! $120 for a flush and ~ $80 for each sensor! I found a site out of Califronia where I can order both sensors for under $100. Will see if I can schedule an AT flush sometime this week and go from there. What is the deal with the spark plug change out on these V6's What is all envolved with it? I have been looking around to find a maintenance Manual for this 2001 sonata but so far I have only found ones that cover up to 1999.

Hummmmmmm? How was it that the sparkplug wires induced a check engine light?

faulty plug wires will cause a misfire code.

HI.. Could you please tell me what you did to solve your problem? I have the EXACT SAME PROBLEM RIGHT NOW.
When I am driving, the engine will give a thud and then it will drop automatically to the 3rd gear.
After that, I can only access the 2nd and 3rd gear. I put an OBD scanner and got 2 errors:
P1529 : Scair Solenoid circuit malfunction
P0715 : Input turbine speed sensor circuit malfunction.(the check
engine light is almost always on). The problem disappears when I
restart the car.

THanks in advance for your reply..

I too have this problem. Any answers as to how it was resoved. I was driving. It made a thump and went into 3rd gear. I could not get it into 4th.
I pulled over and shut off for a few seconds. i restarted it and it did fine. At least for now. I too have the exact codes. I did not clear them yet.
I am at 125,000 miles. I don't know if it is a programed thing to get you in for a transmission service ????

Well, thanks to some info. I got from Duke I went ahead and replaced the input speed sensor and that seemed to have fixed the problem. Granted the problem for me was intermittent, I should know for sure after a few days of highway travel.
When I was searching for answers , I noticed a ton of forums and users posted the same problem but nobody seemed to list how they corrected it. So here is some info for future reference.
The input speed sensor for my 2002 Sonata V6 was part # 42620-39051. I got it from my dealer for 66.41. I called another dealer and it was $80. I thought dealers had the same prices....apparently not! As for the install it was not really difficult once I figured out how to get to the sensor.
There may be a different way, but this worked well for me.
Disconnect the battery and take it out. open your air filter box and swing the top out of the way. There are 3 bolts to remove your lower part of the air box. remove the 3 bolts and lower airbox
There is some linkage that goes right over the sensor. there is a bracket that you need to remove 2 bolts and the bracket will be able to be moved off to the side and you can access the sensor. There are a few bolts on the bracket, you need to just take the ones that bolt straight down(not horizontal). Now before you take off the bolt that holds the sensor look for crud/grit etc. I had a lot that settled there. Once you pull the sensor out , that crud could fall into the opening. I just took a dental pick and loosened it up and blew it off with compressed air. once you take the one bolt off that holds the sensor then remove the wiring harness/plug. It is very hard to unplug the sensor while bolted in.
you should be able to install your new sensor and just reverse the order.
Remember, everything is metric and you will need some socket wrenches I think Sizes 10-14mm. also a few extensions for the sockets.
Hopefully this will help some body else down the road who encounters the same problem.
On another note, I did have my local garage do a transmission flush and that did not solve the issue. I was in need of one, so it is a good idea...however it did not seem to be the root of the problem like some other posts I read .

Sorry for a delayed response, but I am truly disgruntled with my Sonata by now..

The deal is, I purchased the part from Autozone for about 70 bucks, had someone replace the input speed sensor.. and everything was fine for a day.

Next day, I AGAIN get the same freaking check engine light error, even though i replaced the sensor.
Till now, I've been just living with it.. unless there are some other ideas I need to look into.
Would transmission flush or replacing spark plugs help?? Or should I just take it to a hyundai tech?

Well, I did have my trans fluid changed prior to the sensor. I was getting the oil changed and it was only an extra $20 or so....
A few blocks away after the service it acted up. So that did not solve it, but it may have been a combination of them both? The guy said the trans fluid smelled awful. So, who knows. for $20 it would be worth it. I would not bother with spark plugs. I don't think that would have anything to do with it.
You said you had somebody do it for you. Double check the connections.
Also, I don't know if you read my tips for cleaning the area around the sensor....maybe some debris got in there?????
I did read in some occasions the output sensor may be a bit to blame....you may have to consider replacing that too. That one should be easy. Not as much removal to acess it.....
good luck

of all things to buy from 3rd party part companies, electronics is not one of them! For components like this always stick with OE parts

Yeah, Knock on wood....I have had no problem since the new sensor. As it sounds, I would stick with a genuine Hyundai part, as "Quality" as it may sound!
Sounds like the AutoZone route may be a concern.
Let me know if you have questions with the install........

The P0715 doesn't have anything to do with spark plugs. Replace the input speed sensor and clear the adaptive learned values (disconnect battery neg cable for a few minutes)
If the code comes back, then you'll need to check the connector and terminals for correct tension/fit.

Try a Pulse Generator Sensor, i had a similiar problem with my 96 Elantra.

Not sure what the code was when my engine light came on but apparently the car backfired and the mil came on then in the morning it went away. I took it to the dealer and they replaced the speed sensor. This was oct 23 2003 with 60,000 miles according to my paperwork and it was under warranty with the bumper to bumper to 72,000 since the horsepower was wrong in some paperwork and they made up for it by adding to the warranty. Check with the dealer and see if they would cover it if it was the speed senser. If its not under warranty you may have to pay for the diagnostic yourself.

Steve

having the same problem with my 2000 sonata and i am have the input speed sensor changed at a transmission shop and they told me the p1529 code come from the other code for the speed sensor it just tell the ecm to display the check engine light trans control module sends message to the ecm because of the speed sensor well i keep u guys informed on how it works out but it seems to be common with hyundai maybe they have a problem with there transmission and need a recall

well got the car back today and just changed the speed sensor and everything works fine like brand new if u are having this problem i recommand that u change the speed sensor and the car will drive alot better.

hi, im having the exact same problems I had the output (VSS) speed sensor replaced, my car works alot better, it stops better and it switchs the gears without lugging the gears and making me buck as much anymore. It still has the same problem though, but it is not as bad. what I notice the most is there is always a sudden sharp increase/decrease when the gears shift, since the output VSS been replaced the car seems to have a better feel to it when it shifts/brakes, but seems like my orignal problem of the sharp increase/decrease in shifting. If im going uphill at 38 mph, the tech is at 2500-3000rpms at this point, my foot is half way on the gas, and if i push on the gas alil more it wont react fast enough, as if i didnt really press on the gas alil bit more, it is only when i press the gas pedal down in big increments that it will sudden just shoot up to say 5000-5500 rpms and then ill get alil bit more momentem out of it. it revs alot more then i feel the feel the acceration react, then it will jump back down to to around 3500 rpms (it changes gears at this point, use to change gears harsh before the output VSS was replaced) then to 2000rpms if i let go of my gas petal.

I would think the rpms should smoothly raise up, but when i press on my pedal it likes to rev alot be for it starts going, then after it moving everything seems fine, it seems like I need a tune up, but im not sure if it would fix the problem.

also if i going on a flat road, sometimes I hear a sound from the engine if i press on my pedel alot, it sounds like a quick snaping sound, it doesnt happen all the time it all feels like an intimitent problem, but i beleive i do feel a performance lose. The car has 118,000 miles on it, and the car usually has it oil changed on time. Im not sure of the exact cause of the problem, any input from someone will be appeciated. thanks :-/

Edit: Before they changed my speed sensor they put the car on the lift and told me afterward that car said it was going 40mph while the obd reader said the car was going 60mph. after they changed my sensor I don't know if they check out the system again after changing the output sensor. I bought the car at 70K, and recently did a flush of the trans fluids, before this problem i have now though.

Sonata 2001 GLS
- Mike

This post has been edited by SoulSpy: Aug 25 2006, 04:44 PM