My ford mustang gt 2009 keeps giving me this code. After research, I've already put in a new alternator, and a new camshaft position sensor as well, but the code won't go away.

I can't even get my inspection because of this, anyone have any ideas?

 

What alternator did you put in? It's not uncommon to get a bad reman from advance or autozone. If you bought a reman from one of those places then have them test it. They should be able to test it for excessive AC ripple.

Guy I work with has a 1999 explorer. He just replaced the alternator with one from advance auto parts and the truck started running rough and he got the p0340 code. I'd have them bench test the alternator before taking possession.

 

I put in a PA performance alternator from americanmuscle. I also put in a new duralast battery.

 

I would still take it to an oreilly's or autozone and have then test it. I'm sure even Pa performance has diodes that go bad prematurely.

Did you replace both sensors?

 

I replaced the one near the driver's side. I thought there was only one, there is another one near the passenger side?

 

The sensor is almost never bad, so if it's not AC voltage leaking from the alternator, then I'm at a loss.

Have you done anything else to the car recently?

 

Nope, I guess I'll go take it to autozone and have the alternator tested.

 

I had this happen. Drove me ****ing nutz. Even went as far as to replace wire ends/plug that goes into alt. The Advance Auto manufactured alt was bad. Sometimes the alt wont show as bad, because it can be an intermittent failure that will drive u nuts cause they say it tested OK. Eventually I told them I want my $$$ back & they reluctantly agreed. Installed an OEM alt from FORD and all was good.

Every time I have ever tried to save $$$ on a reman alt or starter it has bit me in the ***. NEVER again, OEM as far as those two parts.

 

There is a sensor on both sides. The passenger side was hard to see because of the wiring harness. I had to unplug it when I swapped my cam covers recently.

So, you could swap sensors and see if the code changes. I assume the passenger side will give a different code.

 

My 04 only has one knock sensor.