Electrical ghost-Reduced engine mode

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Woodell14

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Hi all, I have an 08 Yukon and just the other day it started having some kind of electrical issue. I was sitting idling and it just shut off by itself but the radio and AC were still on, just the motor shut off. Tried to crank and nothing. Took negative lead off battery and put it back on and it crunk up and ran fine for about 2 minutes and the the same thing, but this time it would turn over and when it did start it was in engine power reduced mode. Took cable off again and it crank up and ran right for another few minutes and then did it again. Now it’s to the point when it does shut off and I try to start it back it won’t do anything for a few seconds and will finally click frantically like a bad battery and then it will start but be in reduced engine power. I’m no electrician and this is stumping me. Anybody ever had similar issues? Also the alternator and battery and only about 5 months old
 

OR VietVet

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Don't care about battery and alternator age. What quality are they? Does sound like possible grounds problems and/or cables problems as far as clean connections, tight connections and corroded connections. Don't assume that the alternator or battery are good. Test them both and make sure the battery is fully charged when load tested.

By the way, welcome to the forum, 6 years later. Joined and no posts in 6 years? WOW!
 

swathdiver

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If yours were mine I would want to put a bi-directional scan tool on it and pull all the internal codes to see what's going on. Who do you know with a Tech-2? In Florida by chance?
 
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Woodell14

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Don't care about battery and alternator age. What quality are they? Does sound like possible grounds problems and/or cables problems as far as clean connections, tight connections and corroded connections. Don't assume that the alternator or battery are good. Test them both and make sure the battery is fully charged when load tested.

By the way, welcome to the forum, 6 years later. Joined and no posts in 6 years? WOW!
Ok thanks I’ll check them, the alt and battery came from Autozone. I checked most of my grounds but I have two more to check out and clean up that are on the frame on drivers side.
I didn’t realize I had been joined that king haha. I’ve never even really been on here since I did join when I got my first tahoe in 2016.
 
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Woodell14

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If yours were mine I would want to put a bi-directional scan tool on it and pull all the internal codes to see what's going on. Who do you know with a Tech-2? In Florida by chance?
I don’t know anyone with a tech-2 unfortunately. I’m in Arkansas.
I had a buddy hook his code reader up to it but it’s a basic one and only showed an evap canister solenoid or something but that’s been know for over a year now.
 

swathdiver

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Yeah, you'll need a bi-directional scan tool for proper diagnosis. Consider buying a Tech-2 if you are going to keep this car, it's a must to properly diagnose and work on them. They are about $300 delivered, which is about 1/2 the cost of a local dealership's diagnostic fee.
 
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