Alternator controlled by ecm/pcm

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stamp11127

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The following link was provided by "theoldwizaed1" in a thread dealing with a no charge problem. It shows the need for troubleshooting the electronics with the proper tools (scope) that most diy'ers don't have. It also indicates an apparent design flaw with validation of alternator output compared to what is being commanded by the pcm.

 

deweysmith

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He says the light never came on, even with the wiring harness unplugged, but it did! At 24:41 the scan tool shows the "Generator Fault Indicator Light" changed from Off to On.

Also, I always saw the "Charging System OK" in the system check in the menus in the dash and thought "yeah, there's the right voltage in the system, I can see that with the voltage gauge over there… what else would it be checking? Why does that exist?"

NOW I KNOW.
 
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