Hyundai Repair: Code P1372, What can be done to fix the problem?, hyundai santa fe, crankshaft position sensor

Question
I have a 2004 2.7L (V6) AWD Hyundai Santa Fe that recently starting loosing power, checked it with a code reader and code P0335 (crank shaft sensor) and p1372 (segment time acquisition incorrect). I looked into what needs to be done and due to the location and me not having a garage to work on it in, I brought it to a mechanic and he replaced sensor, but when he called me he said it did not fix the problem and he didn’t have the correct equipment to clear the code. I brought the car to another mechanic and he replaced the sensor with an actual Hyundai OEM part and said that the computer was also bad. I had the computer replaced (with a used one I found) and the car ran fine for a few days. While going up a hill the other day the check engine light came on and off, then back on few minutes later and started running rough and a little weak. Hooked the code reader up and code 1372 was showing along with code 0300 (random misfires) followed by misfire codes such as P0301, P0303, P0304, P0305 and P0306. Cleared the codes hoping with the new sensor and computer things were just re-adjusting to there new home. Next few times I drove the car things worked fine. The engine light came back on this morning and the car started acting up and the same codes P1372 and 0300 codes are showing again. What is the new or compounded problem that is leading to these codes? How would I go about fixing it?

Answer
The P1372 code indicates there's too much variation between how long it takes for one cylinder to fire as compared to the others.  Incorrect readings of this nature can cause the ECM to report a false misfire code and can even cause misfires if the problem is bad enough that the ECM cannot effectively determine the position of the crankshaft.  Every time I've seen this code or the P0335 code, the problem has been in the crankshaft position sensor itself.  This doesn't necessarily mean you don't have some other problem causing the code, but will play a part in the advice I'm going to give.

Since the P030x codes weren't present prior to sensor replacement, the suggestion is present that the sensor replacement may have somehow caused an additional issue.  If the sensor isn't properly seated in the hole in the engine block, is loose, or isn't securely connected, this issue and trouble code can be caused.  So if I were to be looking to diagnose this problem knowing the history of the repair attempts, I'd first be looking to verify proper installation.  I'd remove the starter so I could view the area well, and if everything looked appropriate, I'd even entirely remove the sensor for a closer inspection.  

You'll want to choose a most qualified mechanic to be doing such a review.  I find it a little disturbing that you've been to two mechanics already-- this suggests that at least first one may not have been qualified to do the repairs, and this suggestion is supported by the fact that he didn't know that disconnecting the battery would be enough to clear the codes.  Furthermore, the suggestion that the computer was defective followed by a replacement computer not changing any issue suggests that the second mechanic isn't capable of performing proper diagnosis-- he simply (and fallaciously) assumed that since the sensor didn't fix the issue, that the computer must be defective.

If we determine that the sensor is indeed properly installed and that the sensor itself is functioning properly, I'd next want to check two things:
-- I'd want to check the toothed wheel on the crankshaft that the sensor reads.  It's important to verify it's not loose and doesn't have damaged teeth.  With the starter and sensor out of the way, a rudimentary inspection can be done through the sensor hole.  A closer inspection can be done by removing the oil pan, but I'd wait to do this until after the next inspection has been completed.
-- I'd check the wiring to the sensor.  I'd want to check any areas of wiring visible to be sure they're not rubbed through.  Then, I'd also be sure to electrically check the integrity of the wiring between the sensor and ECM.  I'd want to do this based on the schematic, too.  I.e., the sensor may receive power and or ground directly from a source other than the ECM, so it's important to make sure these circuits are intact as well.
Again, though, my suspicion based on the evidence is that there was a problem with the repair that has caused you to continue to have an issue-- so I'd primarily be interested in exhausting all avenues this could have occurred prior to moving to other potential causes.