Hello, my check engine light came on a few days ago while driving home from work. The engine was running perfectly normal, both before and after the CE light came on, so there were no symptoms at the time. Overall the engine was and still is running great. I got just one code, which is P1381. I read in several places that this trouble code (Cam Position Sensor) can be caused by electrical issues, either battery or alternator issues. I checked my battery connections and fixed a slightly loose negative terminal connection, but the code still came back after that, and I also had an engine or shifting issue occur 3-4 times this morning when driving to work. It felt like either a surge or a shifting issue. The RPM needle moved so slightly that I could barely see it, but there was a hard jerk as if down-shifting one gear, which stayed for 5-10 seconds and then jerked back to normal. Today was the first time there has been significant erratic behavior since the CE light first came on 5 days ago. The 2nd time it came on, there was some very mild surging, just once twice, but not hard jerks and much more subtle. This morning was MUCH more noticeable.

Not sure if this will help, but here is the Freeze Frame data from the 2nd time the CE light 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 worked on the negative battery terminal connector a few times before getting it good and tight, and each time I removed it the CE turned itself off. Some of the Freeze Frame data is a bit different the 3rd time, so I'll jot that down and report back with that as well.

 

What year is your car and is it a 4 or 6 cylinder engine? Does your car have a distributor?

 

So sorry that I left out that info! It is a 2001 Honda Accord, 2.3L, 4 cylinder. F23A4 engine
270k miles
Yes, it has a distributor.

By the way, yesterday 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 yesterday. This 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 above, 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.

 

The CYP sensor is in the distributor.

On your generation Accord, P1381 can also be caused by electrical interference from an alternator with faulty diodes.

This attached excerpt is from a Honda Service New article.

 

Thanks for that. I will give this a try. Not sure if this will be helpful, but here is the freeze frame data from the 2nd time it came on, after re-setting it the first 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

 

I skipped to STEP 2 of the troubleshooting article that you included, since the same distributor has been on the vehicle since I got it (probably close to 10 years ago) and it has not been serviced, so the Coil Shield has not been changed in any way.

For STEP 2, I test drove the vehicle for about 10 minutes since that was all the spare time I had at the moment, but the Check Engine light did not go back on until after I re-connected the harness to the Alternator and proceeded to drive it for less than 2 minutes. I was actually surprised that the EC light came back on that quickly, but I guess that means it rules out the Distributor.

Since I don't have a scan tool that would allow me to view the diode pattern, I did a diode check on the Alternator with the following method:
Disconnected the alternator from the vehicle (removed the direct positive cable and removed the electrical connector/harness) and then used the diode setting on my multimeter. With the black multimeter probe on the positive lug of the Alternator, and the red multimeter probe on the alternator body (acting as ground), I was getting around 600mv. With the probes reversed (black on alternator body and red on alternator positive lug) I got no reading at all, which seems to indicate that the alternator is good.

Is there anything else I should test on either the alternator or distributor to fully rule them out...or should I now be looking at the CAM sensor itself or possibly an actual issue with the cam timing or cylinder position?

 

It sounds like it fits the description in the Honda article regarding electrical interference from faulty diodes in the alternator.

 

That's what I was thinking too, but when I tested the alternator with it isolated, it showed a millivolt reading within range for the diodes, and also only allowed the current to flow one direction, so it seems like it might not be the issue. Unfortunately I don't have a scope that will allow me to view the wave pattern of the diodes, so I'm not sure where to go from here.

I may have to just put a new distributor in and see what happens, but I don't usually like to "throw" parts at it.

 

If you're just throwing a part at it, an option is to just replace the rectifier in the alternator. It is held in with screws, no unsoldering/resoldering.

See Section 4-34 and 4-35 of the service manual: https://drive.google.com/file/d/18oT...npH6sdIc_/view

Is it similar to this youtube video:
https://www.ebay.com/itm/30346644105...6g04sFES_8Pq_Y

 

Thanks for the input and for the manual link!
I ordered a new distributor and alternator. The distributor came first, so I already replaced that and it did not fix the issue. The CE light still came back and the intermittent driving issues did not change at all.
The new alternator arrived, so I will be replacing that tonight and am hoping that fixes the issue. I will post an update here afterward.