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Discussion Starter #1
I just picked up a '15 ST3 and the sub isn't working, sound from all other speakers but nothing from the sub. Thoughts?
 

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Well the possible causes are the sub woofer itself, the circuits between the sub woofer and the amp or the amp. If you don't see any obvious connection, circuit or pin fit issues then I would go into circuit testing such as continuity, short to power, short to ground, shorted together, etc. If no issues are found then it is likely the sub woofer, if all other speakers are working than the amp and powers/grounds to the amp are most likely working correctly.

I think the amp is able to set codes through the APIM or the APIM is able to set codes against the amp.

Sounds like a trip to the dealer wouldn't hurt in this case.
 

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2017 Ford Fusion Sport
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To the dealer you go. Warranty that sob real quick and save yourself the headache.
 

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Discussion Starter #4
Well the possible causes are the sub woofer itself, the circuits between the sub woofer and the amp or the amp. If you don't see any obvious connection, circuit or pin fit issues then I would go into circuit testing such as continuity, short to power, short to ground, shorted together, etc. If no issues are found then it is likely the sub woofer, if all other speakers are working than the amp and powers/grounds to the amp are most likely working correctly.

I think the amp is able to set codes through the APIM or the APIM is able to set codes against the amp.

Sounds like a trip to the dealer wouldn't hurt in this case.
for these vehicles, does the amp power the speakers as well, or are they powered by the indash unit?
 

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@Cowlynz is correct, the amp powers the speakers but not in the traditional way one might think. On Fords the amp is a module just like a PCM or BCM, that communicates on the network. So it takes all the sounds from the APIM and relays them to the speakers, but it does not amplify it like it does with the subwoofer. The AMP also shuts down the sub and the rear speakers for things like voice recognition, phone calls, etc that only come through the front speakers.
 
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