need help on a p0340 code. don't think its alternator
06-21-2014, 08:15 PM
#1
Thread Starter
Join Date: Oct 2006
Posts: 30
need help on a p0340 code. don't think its alternator
So I just recently fixed a leak from the headers to the mid pipe and was doing the drive cycle but when I got back I plugged my reader in and got the p0340 code for the camshaft sensors. The part i dont like is that i do have hot rod cams installed on my car but have been on there and fine with no codes for two years. So I searched and got that a lot of the time it seems to be the alternator. But I did the simple check of putting a volt meter to the battery and it was at 12.2... had a friend start the car and voltage climbed to 14.5. It stayed at 14.5 while the car was on even when holding the rpm's around 2500. This should mean my alternator is ok right? Looked at the camshaft sensors themselves and nothing seems destroyed or burnt unless they just went bad? Really hoping I don't have to get back into the cams and rollers.
06-25-2014, 01:34 AM
#3
5th Gear Member
Join Date: May 2007
Location: Central Texas
Posts: 2,388
Not necessarily. The voltage for a failing alternator can vary and change when in use. It may read 14 volts at idle, and while you rev the engine. But drive it 30 miles or so, and during that time, it may dip into the 12's and that's when the code will be thrown.
When does the CEL come on? Is it right away after clearing it, or randomly when you drive it?
When my alternator started going out, it was after my last run at the track, and the CEL came on, P0340, first time ever. I cleared the code, drove home, and then a few days later, it came back on again. I started watching the voltage as i was driving, and it would start up higher, like in the upper 13's, then eventually get lower into the mid-to-upper 12's, and throw the code.
It was the alternator that caused my issue.
So, just checking the voltage at idle and in the driveway does not mean your alternator is good.
(Also, since your signature says "GT", I assume you posted this in the wrong section and do indeed have a GT and not a V6 where this is an issue.)
When does the CEL come on? Is it right away after clearing it, or randomly when you drive it?
When my alternator started going out, it was after my last run at the track, and the CEL came on, P0340, first time ever. I cleared the code, drove home, and then a few days later, it came back on again. I started watching the voltage as i was driving, and it would start up higher, like in the upper 13's, then eventually get lower into the mid-to-upper 12's, and throw the code.
It was the alternator that caused my issue.
So, just checking the voltage at idle and in the driveway does not mean your alternator is good.
(Also, since your signature says "GT", I assume you posted this in the wrong section and do indeed have a GT and not a V6 where this is an issue.)
08-23-2014, 10:51 AM
#4
Cut & Paste Expert
Join Date: May 2007
Location: NW Arkansas
Posts: 13,322
If some of your diodes are bad, it can look like 14VDC but be putting a lot of AC
ripple in the system. My Alternator recently took a carp but was putting out
14+VDC but the silly scope showed a lot of AC ripple on it and it had multiple
bad diodes in the diode cluster. Voltage is not an honest way of determining
alternator health...
A good shop with a multi-meter can check the diodes from
the rear of the case thru the cooling slots without disassembly.
ripple in the system. My Alternator recently took a carp but was putting out
14+VDC but the silly scope showed a lot of AC ripple on it and it had multiple
bad diodes in the diode cluster. Voltage is not an honest way of determining
alternator health...
A good shop with a multi-meter can check the diodes from
the rear of the case thru the cooling slots without disassembly.
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