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Got an 05 gto auto 223,000 miles all stock. About 2 days ago the check alternator message came on, it comes on then goes off after few seconds, it will do this through out the whole day of driving random times. i took it to autozone and oreileys back to back yesterday and their free test device they go outside to car with both guys said battery and alternator are good. Before the dash message came on for about a month or maybe longer sometimes when starting the car it will crank slow like e\weak but will start up though.

Now today had to goat towed to house because on the freeway all sudden besides the check alternator message the abs fault/trac off came up to and the gauges needles would go haywire like down and up to normal back and forth for about 5 more mins of driving then eventually power to the stereo and all gauges went off etc then car started to stall, i guess the fuel pump wasn't getting electric power right? anyways pulled over and had it towed.

Im charging the battery now it dead wont crank just clicks, but you guys think a bad alternator or i hear about checking the ground cable from it? where is it at and anyone know where it goes to from the alternator to where? thanks
 

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Alternator has no ground cable. It grounds by bolting to the block.

1) check battery connections. You may have corrosion under the terminals. Clean them to be sure.
2) after doing this and charging the battery, access the hidden menu on the dash (search it) and toggle till you get to battery voltage. More than likely it’ll read 13.8-14.2 when cold. As it warms up it will start dropping. 13.2 is usually what it will sit at. If it starts getting below 12.5v when hot then the alternator is bad. Mine did this. Charged when cold. Stopped charging when warmed up. The check ALTERNATOR light flashed a few times several days before it ended up staying on when the car gets warm. I put a new delco unit in it and it’s good now.

Do not buy a reman alternator. Even the delco reman is no good. I went through three remans. If you like to change alternators, then just ignore my advice.
 

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Alternator has no ground cable. It grounds by bolting to the block.

1) check battery connections. You may have corrosion under the terminals. Clean them to be sure.
2) after doing this and charging the battery, access the hidden menu on the dash (search it) and toggle till you get to battery voltage. More than likely it’ll read 13.8-14.2 when cold. As it warms up it will start dropping. 13.2 is usually what it will sit at. If it starts getting below 12.5v when hot then the alternator is bad. Mine did this. Charged when cold. Stopped charging when warmed up. The check battery light flashed a few times several days before it ended up staying on when the car gets warm. I put a new delco unit in it and it’s good now.

Do not buy a reman alternator. Even the delco reman is no good. I went through three remans. If you like to change alternators, then just ignore my advice.
Above your saying the "check battery light" flashed stayed on is this different than the check alternator that im getting? or is the check alternator the only message we get on these cars and its what your meaning?
 

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Bro I hate to be the bearer of bad news but this just happened to me it's NOT the battery it's the alternator. As you're driving things start going haywire, the abs warning comes on, then the traction control goes out, then the dash display starts flickering, the windows stop working then the radio/security system becomes disabled then ultimately it dies as I'm driving all this madness is going on then as soon as I was about 3 minutes from home it completely died. I had to get it towed to the mechanic though. The worst part about my situation was I couldn't get the windows up I had no juice to put em up. My alternator ultimately failed because of a leaking PS hose the hose is right above the alternator when my guy removed it he showed that it was covered in PS fluid. Now last Friday I had to replace the battery luckily I was close to an auto repair shop that carried interstate batteries. By the way I own a slightly modified '04 with a little over 66,000 miles on it. These cars are quirky. Keep us informed of your situation, you never know it may just be the damn battery.
 

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Bro I hate to be the bearer of bad news but this just happened to me it's NOT the battery it's the alternator. As you're driving things start going haywire, the abs warning comes on, then the traction control goes out, then the dash display starts flickering, the windows stop working then the radio/security system becomes disabled then ultimately it dies as I'm driving all this madness is going on then as soon as I was about 3 minutes from home it completely died. I had to get it towed to the mechanic though. The worst part about my situation was I couldn't get the windows up I had no juice to put em up. My alternator ultimately failed because of a leaking PS hose the hose is right above the alternator when my guy removed it he showed that it was covered in PS fluid. Now last Friday I had to replace the battery luckily I was close to an auto repair shop that carried interstate batteries. By the way I own a slightly modified '04 with a little over 66,000 miles on it. These cars are quirky. Keep us informed of your situation, you never know it may just be the damn battery.
I cleaned the battery post yesterday morning, they weren't corroded but i wire brushed them anyways and made no difference as the final issue happen this evening pretty much exactly same symptoms you had i had too.

I'm going to do want the above guy says to do and go from there.
 

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Yeah looks like bad alternator, did the hidden menu test and same time had a muli-tmeter on the battery after letting it idle until hot normal temp and gradually went down i turned car off when it read 12.2 volts and that's with no accessory's on no headlights no radio no lights etc. ordering a alternator now thanks for help.
 

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You may very well have a bad alternator, but while you're at it do yourself a favor and check all the main power and ground cables as these are common points of failure that cause electrical symptoms. The battery post terminals tend to go bad after many years, if they are shot it's possible to replace them without having to replace the entire cable (as long as the wire inside isn't corroded, if it is then change the whole thing). Also the main positive cable to the fuse box and the grounds to the engine and frame.
 

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Check the power lead that runs from the stud on the back of the alternator to the battery. Particularly the strands that go into the terminal.
 

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There are 3 grounds stacked on the passenger wheel house, the vehcials are painted (of course) prior to the ground installation and (of course) the paint remains. It's common to loose that connect and it will do all manner of off the wall crap. Clean that ground and see what happens. The dash will wig out at low voltage, meter the running level (should be @14) and the stopped voltage (@13) Leave the car over night, hit the stopped voltage again, should not have dropped more than 1 point if at all, if more you likely have a leak to ground, good luck.
 
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