Transmission wont shift after replacing thermostat

Tiny
SWREICHARD
  • MEMBER
  • 2003 HYUNDAI SANTA FE
  • 2.7L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 112,000 MILES
I just purchased this Sant Fe, and it would not heat up to normal operating range. The check engine light came on, and trouble code referenced not operating to correct temp. I changed the thermostat, and this fixed the operating temperature issue. As soon as I changed it, I went on a test drive and was going approximately 60 mph when the vehicle shifted out of overdrive on its own. I slowed and stopped, turned around to head back towards home, and the vehicle will not come out of 3rd gear. Its an automatic transmission, and does not down shift, or shift into overdrive, remains in 3rd gear even if come to a stop and take off again. The trouble code now showing is p1529. After letting the vehicle sit overnight temps cool, (the vehicle never overheated) and cool to outside temps, I started the vehicle and went driving. Same thing, the vehicle shifts fine when cool, but once the engine reaches normal temp, shifts out of overdrive, into 3rd and will not shift out of 3rd.
Do you
have the same problem?
Yes
No
Thursday, January 30th, 2014 AT 3:46 AM

4 Replies

Tiny
HMAC300
  • EXPERT
Hav a trans guy look at this it may be a valve body problem or the overdrive unit is no good. Seals go bad and act up when they get warm
Was this
answer
helpful?
Yes
No
Thursday, January 30th, 2014 AT 6:05 AM
Tiny
MLDANIELS2000
  • EXPERT
Hyundai has a computer reprogram service bulletin for that issue. See dealership for possible reprogramming. May cost around $100+.
Was this
answer
helpful?
Yes
No
Thursday, January 30th, 2014 AT 7:11 PM
Tiny
SWREICHARD
  • MEMBER
Thanks for the info thus far. I went to another auto parts store and tried a another scanner. In addition to the p1529 code, this reader also showed p0715, and p0734. The p0715 is the input speed sensor, which is about $80 for the part. I believe its right on top of the transmission, and would not be too hard to replace. I am wondering if when I changed the thermostat that the leakage from it, somehow shorted out this sensor? Wanted to get thoughts, as if I purchase the $80 sensor, of course I cannot return it. Would it cause the transmission to not shift once warm and remain in 3rd gear, and not allow it into overdrive? Is it worth the $80 to try it before going to a dealer I guess is the bottom line question for the experts? Thanks
Was this
answer
helpful?
Yes
No
Friday, January 31st, 2014 AT 3:39 AM
Tiny
MLDANIELS2000
  • EXPERT
Most possible the speed sensor is causing the issue. Reading the possible causes of 3rd gear lock out is from that sensor. Go ahead and replace it then have the codes cleared.
Was this
answer
helpful?
Yes
No
Friday, January 31st, 2014 AT 6:32 AM

Please login or register to post a reply.

Recommended Guides