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Hi,

I recently purchased a used 2010 Forester with about 135k miles. I had it checked out by 2 separate independent mechanics before purchasing and neither identified any significant issues. A month after purchase, the check engine light started going on along with a flashing cruise control light and vehicle dynamics control light. Over the past six weeks, this has occurred repeatedly in a few different situations: (1) Upon a failed attempt to start the vehicle; (2) when the car stalls upon an attempt to accelerate from a full stop when waiting in traffic; (3) when the car stalls when at a stop without attempting to accelerate; (4) when the engine shakes/knocks and doesn't stall - this typically occurs when at a stop.

The car has always eventually started, it may take 2-3 tries after the lights go on. The lights eventually clear themselves, usually the next day or in a couple of days. This happens over and over again.

I previously associated the issue with the AC kicking in, but recently have had the same issue occur when the AC was off.

According to Autozone, the error code is P0340 "Camshaft Position Sensor A Circuit" (the same code is stored in memory multiple times)

I took it to a mechanic shop that specializes in Subarus. They couldn't find a problem other than a purported bad sector in the battery. I had the battery replaced, which has had no impact on the issue.

I took it to the seller (a different mechanic shop) and he said it's most likely not a camshaft sensor issue, and said it could be an oil issue, and topped off the oil. This has had no impact on the issue.

I recently took the car in to the local Subaru dealer for the passenger-side airbag recall. At that specific time, the lights were off. But they did a check of the car after the recall work, and they did not find anything wrong.

Anyone have experience with this type of issue?

Thanks.
 

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2004 FXT 4EAT
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Is it a Turbo?

I get some camshaft related error codes, but they are different from the P0340 you're getting. I start getting the error when I'm due for an oil-change. I use Synthetic Oil, so I don't change it at frequently as one would with "regular" oil. But the error stops as soon as I've changed the oil.

Since changing the oil & filter isn't horribly expensive (especially if you can do it yourself), it may we worth doing that. Just to rule it out.
 

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@GuusV could be right, although that does throw a different code. It certainly can't hurt.

Since they know subarus, I take it that they checked the cam sensor? It would require checking with a scope and even then it could be intermittent.
They can go bad but I'd be reluctant to just replace it without knowing it is bad.
 

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2012 SH Manual Diesel
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Did you manage to ask any of the mechanics what they actually checked?

Saying they “checked”, could mean they looked at the dashboard for a CEL, or did a workshop diagnostics procedure, to load/stress/heat testing a part. Not everyone’s effort or care-factor is the same (and that applies to all professions). And in many cases it’s inversely proportional to the size of the company, pay grade, and level of responsibilities, so talking to the Manager means very little.

I would never assume any person, no matter their title, years on the job, or company they worked for, to have automatically done the most thorough job possible. Because it rarely ever happens these days (chargeability). If they did, they would tell you exactly what they did, and to what extent they went to to isolate the problem (people who are conscientious are also conscious about what others may think of their work. So they do want you to know that they actually did try their best to source the issue).

To at least have a proper look, they should have tested voltage and resistance of wiring harness to and from the sensor, checked that the sensor was clean and seated correctly, looked for corrosion on all plugs and connectors, and as Remco mentions, waveform tested the sensor.

If there are any other electrical components on the same line, they could also be checked, in case they maybe be causing a voltage drop.

Also look for any new aftermarket electronics that might be fitted to the vehicle, as they could cause an interference with electrical sensors.

PT Cruisers apparently had lots of problems with their camshaft sensors, which caused a lot of distress for owners (even though it was a easy fix). It would be worth searching for any history of issues with that part on your model.

If you’re handy, it might be worth doing some trouble shooting of your own. That way you know exactly what has been checked, and will have a better idea if your mechanic or dealer is giving you the run around, or flat out completely doesn’t know.
 
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