Active fuel management

Zorba150

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Active fuel maintenance:
Before going into it heavy, is there anyway to troubleshoot the AFM on a 2009 Chevy Tahoe 5.3? While driving it stays in 8V But when decelerating the MPG go up but instead of going into 4V it stays in 8V even on the highways with cruise control on it still stays in 8V, It worked a month ago and it was working fine, so just want to know if anybody knows of any troubleshooting like maybe a Fuse, a wire harness anything else I can look at before the inevitable. Thanks for any help!
 

zora

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If no check engine light on you need an advanced scan tool to see what the ECM is doing.
 

Zorba150

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Thanks, no engine light , I’ll be taking it and have a checked, just noticed there’s no pick up and go on the thing anymore👍🏻
 

Zorba150

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If no check engine light on you need an advanced scan tool to see what the ECM is doing.
OK just got back from The Mechanics, he put it on the scan it noticed that the ECM kept asking for 70% power, alternator kept giving it and then shut down,then give it and I’ll shut down again Change the alternator I haven’t taken on the expressway yet or high speeds . I forgot to mention before that my service charging system Warning was coming on also, let you know if the AFM starts working? One more thing at what speed does AFM kick in.
 

zora

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It's not based on speed, the computer determines the load on the engine.
 

Zorba150

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It's not based on speed, the computer determines the load on the engine.
I may not be saying it right? ,he said the computer wasn’t getting enough voltage, He said the computer would be asking for 70% the alternator would give it 70% and then I would shut down and it would do that off and on, he said that there was nothing else showing up on the scan except the alternator?What do you think I would appreciate the thought.
 
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zora

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You asked what speed AFM kicks in and that was the question I was responding to.
 
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