JustangGT

Hi all,

I'm on a road trip and am several hundred miles from home. I have a check engine light on and checked the error codes. I'm getting a P0340 - Camshaft Position Sensor "A" Circuit.

I tried replacing the sensor and then cleared the codes, but the light came back.

It still runs and drives, but it has a intermittent surge/ hesitation in the engine on acceleration that seems to be getting worse.

Any advice? Things to check? What to look at? How to fix it?

I am very mechanically capable but have no tools, garage, etc. here and have a long drive home in a few days, so timely advice is greatly appreciated.

Thanks!

houtex

You swapped the sensor and still there? Did you left /right swap, or just get a new one and swap it directly?

Reason is, I'd like the test of L/R swap to see if the problem moves after clearin' the codes.

After that, it's wiring itself, maybe it's chafed, or maybe the battery/alternator's not happy, the connector's not happy, or the PCM is mad.

Don't think it's mechanical. That will produce a different code regarding differential or something (the timing doesn't match the left/crank sensors, in this case if it were that on the right.)

Battery should read 12.6 volts if fully charged, not running, car off. Alternator should put out about 14 volts when running, checked at the battery. Grounds could be a problem, of course, check those. Rust/loose grounds will make weird things happen.

Get thee a can of contact cleaner and use it. Did this on my motorcycle when it went nuts and fixed it right up. Spray in, maybe agitate with a little soft brush... magic. For the bike anyway. I'd think maybe for the car too...

Not sure I helped, but that's what I got.

JustangGT

Hi houtex,
Finally getting around to updating on this.
I made it home safely and was able to fix the issue. It took a little while since after I got back, the car had to go into the body shop for 2 weeks.

New sensors didn't fix the issue, and all of the wiring was good. I'd clear the code from the computer and it'd come back immediately. There was also a good amount of engine surging that would happen during cruise.
But, I found some info online while searching around, and a few people were saying that they had the same codes and it was caused by a bad diode in the alternator.

About a week ago, I installed a 200 amp alternator with an upgraded charging cable. The code has since not returned (it was probably cleared from disconnecting the battery), and the engine performs better than it has in a long time.

I have an onboard computer reader that bluetooths to my phone, and am able to see voltage.
With the old alternator, it would fluctuate between 12.5v and 13.5v during cruise. With the new alternator, it regularly sits around 14.0 - 14.5v.

So, as far as I can tell, the issue was purely with the alternator, and it was causing the code. But it seems to be fixed now.

houtex

Right on. Electrics on these cars is kinda critical for sure! Glad you got that figured!