Check Engine Light turned on with code P1381?

Thanks for your response, Ken. Before I saw your reply, I had done some other research online and saw that some people suggested double checking battery terminals and cables, as well as the alternator, since they said this code can sometimes be triggered by voltage issues. There was some corrosion on the terminals, but not much, and the negative battery cable was not 100% tight, so I took off both terminal connectors, cleaned the connectors and the terminals, and put them back on. Then I started the car so I could check the voltage at the battery while running, for the sake of checking the alternator. The voltage was 14.35 with the engine running and no accessories on, and with the headlights on and blower fan (just fan, not AC) it was 13.95. I also went ahead and plugged in my code reader while doing this and noticed that the check engine light turned itself off and the reader said there were no codes, so I guess the ECU no longer saw the fault and cleared the code on its own.

I thought I was in the clear, but then when driving home from work the same day, after about 45 minutes of driving, the CE light came on again. The difference this time was that I did notice some engine surging about 2 different times after the CE light had come back on, but I still had another 30 minutes of driving and the engine felt fine for the rest of the drive.

Anyway, not sure if any of this information helps or perhaps points to something other than changing out the Cylinder Position Sensor or repairing its wiring.

Thanks!

Yes, still P1381. No other codes.
Here is the freeze frame data from the 2nd time the code came on:
FUELSYS1: OL-Drive
FUELSYS2: N/A
LOAD_PCT(%): 16.1
ETC (F): 181
SHRTFT1(%): 0.0
LONGFT1(%): -1.6
MAP (inHg): 4.7
RPM: 1951
VSS (mph): 50
IAT (F): 122
TP(%): 9.8

(I did not save the freeze frame data from the 1st time the CE light came on)

See answers to your questions below.

RPM: 1951 - was the engine at a high idle?
No, I was on the freeway when the CE light went on, and I think 2,000 RPM's is typical for 50-60 MPH for my vehicle.

VSS (mph): 50 - were you driving it at 50 MPH when you did the scan?
No, I did the scan when I got home, after the CE light had already come on, and the freeze frame said 50 MPH

IAT (F): 122 - do you live in the hot desert?
No, I'm in Texas, but it was not hot out at the time. Maybe around 60 degrees or so.

Sure, I can do that. I added a battery terminal shim/cap to my negative battery terminal, since it could not be tightened 100%, and when I started the car after doing that the CE light had gone away. I'm surprised that just disconnecting the negative cable would reset the CE light, but if/when it comes back on, I will check it again as you mentioned and report back. Thanks!

I re-checked with a code reader as you described, key on, engine off, and got the same code P1381 and no additional codes. Here is the freeze frame data from the 2nd time:

FUELSYS1: CL
FUELSYS2: N/A
LOAD_PCT(%): 49.8
ETC (F): 181 (exact same as last time)
SHRTFT1(%): 0.8
LONGFT1(%): 1.6 (was -1.6 last time)
MAP (inHg): 14.7
RPM: 2080
VSS (mph): 53
IAT (F): 126 (was 122 last time)
TP(%): 16.1

Also, two days ago when driving home from work, I suddenly had some more serious surges from the engine, with the RPM rappidly jumping up around 500RPM 5 or 6 times in a row. Then it returned back to normal. It did that about 2 different times that day. The next morning when driving to work it did not do that at all, but one time it felt like it downshifted a gear for about 5-10 seconds like I described previously, but no noticeable change to the RPMs during that time. Again, not sure if it is actually down-shifting, but that's what it felt like. Either way, the rapid surging that happened yesterday was a much bigger deal.

Yesterday when driving home from work, and this morning when driving into work. No issues at all.

Fixed. I replaced the alternator and so far, have driven over 150 miles and no Check Engine light and no engine surging or drivability issues whatsoever.
Previously the CE light would come back on within a few miles of driving, and the surging/drivability issues would start happening within anywhere between 5 30 miles and continue at random for the duration of the drive (my commute is 1 hour+).

I was trying to avoid sending in the ECM, due to both cost and the fact that my commuter vehicle would be out of commission during that time, and some research showed that a faulty alternator could cause the suspect sensor to malfunction, triggering the code and other drivability issues. So I decided to try replacing the alternator, especially since I could return it for a refund if it did not solve the issue. I don't usually like to throw parts at the car and I always try to avoid doing that, but sometimes it is the best option, especially when it is a part that is fairly easy to access and replace on the vehicle. Luckily the issue was fully solved by the new alternator.

Anyway, I just wanted to give this update for the sake of others who may research this issue in the future.