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Discussion Starter #1
I have been trying to track down an electrical issue with my Terrain. Im getting 15-15.5 volts. I have replaced the alternator, the battery and the negative battery cable with current sensor. I have also tested for parasitic draws and came back with nothing significant. When i unplug the electrical plug from the alternator my voltage drops to about 13.7-13.9. My interior lights pulse in either scenario. I made sure the battery is fully charged. sometimes randomly when i first start the vehicle i get steady voltage 13.9-14 for about 20 seconds then it goes back to eratic voltage.
The problem exists with or without the aftermarket amp and capacitor.

 

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There are 5 separate programs that the ECM can run for charging.
The ECM can command the alternator to charge at max depending on battery, ambient temp, amp draw, etc. etc.
If your alternator is overcharging you may have an ECM problem.
Are you getting a trouble code?
 

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Try disabling your aftermarket stereo, and see if that cures it.
 

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Discussion Starter #4
There are 5 separate programs that the ECM can run for charging.
The ECM can command the alternator to charge at max depending on battery, ambient temp, amp draw, etc. etc.
If your alternator is overcharging you may have an ECM problem.
Are you getting a trouble code?
I do not have any check engine lights. I have attempted to pull codes anyways with the scanner at advance auto and nothing comes back.
 

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No CELs, the dealer will tell you that you vehicle is operating as it should...even though you disagree.
 

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Advance will only check P codes usually, maybe ABS codes. You need a full scan of all 4 code families which are P,C,B and U to fully see what's going on. U codes are computer communication codes for example.
ECM ground is another to check.
BlueDriver is a phone based tool that will read all 4 families for $100 . Good scan tool is more important than a socket set.
 
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DUDE, That's a Cap your going to see anywhere from 14.9+ with the engine running all the way up to a shocking 20v yea it will make erratic readings but that's really what you want out of a cap because its going to pick up that ac voltage off the alternator I wouldn't be surprised if u saw it go all the way up to 20+ volts with the motor running you really gotta check the dc voltage off the battery without the cap.
 
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