screamingyellowgt

05 gt with code p0340. sensor changed 3 times, bucks and runs rough in colder tempratures(for florida)... saw a post that said alternator going bad screwing up the sensor but I checked the alternator at work and its good... had similar problem on my 99 gt and it turned out to be coil over plugs. anybody have any insight as to what this may be? if you need more info, let me know

Simon1

How did you check the alternator at work and what were the results?

Changing the sensor won't help. Guys have done this several times and they end up getting an alternator.

screamingyellowgt

I work at the chevy dealer (go figure)... we have a handheld device that checks battery, starting and charging system. it said all was good.

Art161

I suggest having the charging system and battery checked using something other than a handheld device. Those handhelds are notoriously bad, and often they are not sent out to be checked on a routine basis.

A service advisor at my Ford dealer checked my battery using a handheld device. It showed good charge, battery okay. After I turned my headlights on for two minutes, with the engine off, it showed needs charge, battery okay. When the service advisor sent the car back for the techs to check it on their big tester, it came back as battery unable to take charge and unable to hold charge. They replaced the battery under warranty.

I spoke to the service manager. He got back to me, and said he had sent all of the handheld devices out to be checked. Two of them were faulty.

Nuke

When was the last TB and MAF cleaning? Fuel system cleaner thru the tank?

Simon1

It needs to come off the car and put onto a real alt testing machine.

screamingyellowgt

never had tb or maf cleaning, it actually has 60,000 and change miles and I put k+n air filter in it.bought it with 31,000

808muscle

Yeah get in there and clean those two items. If that doesnt cure it, just get a PA alternator and that will fix it. Our year cars are famous for crappy stock alternators.

moosestang

^^^^This. A handheld isn't going to show a bad diode.

calistang05

Did the same in my 05 a year ago changed the sensors both sides and didn't fix the problem, took it to Ford and it was the thortle body had it replaced and now it runs fine.