QuestionMy Sante Fe is a 2001 with the v6 and only front wheel drive. The dealership told me the input speed sensor was bad about 6 months ago. I purchased a new one replaced both the input and output speed sensors to be safe. Car drove great until today. Its doing the same things it was then (6 months ago) slamming into gear, locking into high gear at stop sign.
I took it to auto zone got codes P0715 P1529 P0755 P0760. I am thinking since one of the codes is the input speed sensor again, maybe thats it. But are these codes related? If I replace the sensor again should that take care of it? Why did a new input sensor oem Hyundai part go bad again? Are there bigger issues? And the two shift valve codes what are they? I assume those valves are in the transmission and are not something I can do myself?
Please help!
AnswerHere's what your trouble codes mean:
P0715: No signal or improper signal from input speed sensor.
P0755: Open or short in underdrive solenoid circuit.
P0760: Open or short in second solenoid circuit.
P1529: TCM request for check engine lamp to be illuminated.
You'll need more than an input speed sensor. In fact, it's possible that you won't need the speed sensor at all-- the P0715 code could simply be left over from before the previous repair if it wasn't cleared. The symptoms you describe are consistent with any serious problem found by the transmission control module (TCM)-- it turns on the check engine lamp and shifts the transmission to third gear and keeps it there until the ignition is turned off. When restarted, the transmission will again operate normally until a problem is again detected.
First, disconnect your battery for a minute or so to clear the trouble codes and then take the vehicle for a test drive. This will tell us what problems are currently occurring.
-- If the vehicle drives normally, the problem is intermittent. While it's possible your speed sensor could be defective again (just like anything else, every once in a while you get a bad part), that's a very unlikely scenario. More likely is that the code was simply still in memory form 6 months ago.
-- If the symptoms occur again, reread the diagnostic trouble codes and diagnose those that are present. I'll caution that many times these sorts of problems are intermittent, so it's possible that anything not present now may return in the future.
For P0715, inspect the wiring in the vicinity of the input speed sensor. If okay, replace the sensor.
For P0755 and P0760:
I'll first note that power is applied to these two solenoids and the overdrive solenoid through one supply wire. Just going off the fact that only these two solenoid codes are present, I'd suspect a problem in the splice in the power wire (inside the transmission) for these solenoids.
-- If the problem is continuously present, check the circuits for these solenoids with an ohmmeter. The solenoid or wiring could be open, or it could be shorted to ground. Unplug the TCM during testing. If you don't know whether the problem is in the transmission or external harness, you can unplug the connector from the transmission and test each portion separately.
-- Visually inspect as much of the wiring harness as reasonably possible between the connector on the outside of the transmission and the TCM. The TCM is located under the center of the dash. You'll be checking for anywhere wire insulation may have rubbed through, causing the wire inside to make contact with a metal object. (Chances of this being the problem are low).
-- If you see no wiring issues, I'd recommend replacing the underdrive and 2nd solenoids as well as the harness inside the transmission. It'll be enough work that you'd rather not chance picking the wrong component inside the transmission.
You may be able to do this yourself, but it won't be easy. You'll be working in tight quarters. It'll require removing the cover from the front of the transmission and removing the valve body.
Hyundai has very good technical service bulletins regarding the repair of vehicles with solenoid trouble codes. For this reason and to get access to the scehmatics to assist your electrical testing, I recommend you register for a free account at www.hmaservice.com. The bulletin contains much more information than I've been able to present here.
