Got a P0340 CEL code what to do

[Va. Stang]

I've been having the same issue with the P0340 code coming up. Does it every so often. Not sure how to check which it is between alt. and cam sensor. My warrenty is up but I don't want to buy a alt. then find I need a cam sensor

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[smiley2000]

My 2005 Mustang GT started to display the P0340 code 2 weeks ago. I cleared the code twice and it came right back. After researching the error code over the internet, I decide that I will change my Alternator in the next couple of weeks. Well over the Memorial Weekend, I notice my dashboard lights getting dim by the minute, then my radio and all the lights shut off. The car stayed on I was lucky I still had battery power. I was not too far from my girlfriends house and drove it there. It sat stayed in her driveway 2 days. I had to wait until tuesday to get a new Alternator. My Mustang GT is out of warranty and I purchase my alternator from Auto zone. It cost me $214 plus $50 for the core exchange. The alternator is 135 amp verse the Ford stock Alternator is only 130 amps. The only problem it was special order from Autozone. So a long story short..... you have about 2 - 3 weeks from when you get the P0340 code to when your alternator fails.

[Rallek]

Repeat of the previous post. I bought an alternator from Autozone for $214. The alternator is pretty easy to get off the car. It took me about 15 mins. I took it to Autozone, it tested 'dead', and I ordered a new one. Took a day to get the new one, and I was back on the road.

I was getting 'jerky' power when accelerating slowly for about a week before the alternator quit. One night while driving around, I got the check engine light then about a half-hour later, as I was pulling into the house, the driving lights turned off, the ABS light came on, then the traction controll turned off. It seemed like, as the ECU was losing amprage, it was shuting down various systems. I turned the car off, then tried to re-start it with no avail.

[Davidgt05]

I changed my alternator and it fixed the problem. I got the the same codes and the TSB about the alternator. Car run great and I have UDP and Cold intake(CL)

[stangcrazygirl]

I just purchased a 05 Mustang GT 3 days ago and now its doing the same thing, p0340 code. So, from what I read I just need to buy a new alt also? I have no warranty of course.

Thanks, Chandra

[Feng Houzi]

My car did this aexact same thing, I cleaned the throttle body out (wasn;t even that dirty) and it fixed my problem... the first time I got the code p0340 was over a month ago... my alternator is still running strong... Check the throttle body first... thats a free fix... then go with alternator. I'm waiting for mine to die now that I jinxed myself...

[Boozshey]

I get it every couple months. Clear it and nothing happens. First starting after my bama tune. I'm not to worried about it. If I hurt the engine it will be my excuse for stoking it...

[SirKnightTG]

It's the alternator if your voltage starts to dip in the low 13's and/or 12's. I had this code, would get some hesitation/bucking (mis-fire) and I could watch my voltage (with my radar detector and Aeroforce gauges) go all over the place. Replaced the alternator and all is good. I'd also watch the misfire reading in my aeroforce gauges count up most of the time when it would buck.

[mac10chap]

i was getting those codes also. i ended up changing out my cam position sensors with new ones purchased at autozone. still got the codes. turned out being an issue with my brenspeed tune. it was running too rich and throwing codes for the camshaft position sensors as well as the O2 sensors.

[Daniel60]

any updates on this I now too have the code. Ford said I have a bad ecm on memory and will not exchanged it because of my chip. it took five years to get this why? anyone?