Maybe they use the same voltage regulator in the ECM for the 5 volt ref. and the data voltage.
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There are a lot of things on a 5V reference supply on the other 2 connector that you may need to disconnect or inspect on any car ,but before going after power , grounds , and bus circuits, if you get an older Chrysler product with Motorola 3 three connector ecm that you have trouble with ecm communication, scanner pid displays becoming NA, ASD and fuel pump relays going on and off randomly, the SKI key light on cluster, fuel gauge going to empty, Turn the key off and unplug the middle ECM connector 2, then turn key on and see if your fuel gauge now works, the SKI key light goes out , and the pcm communicates, go under vehicle and have a look at the oil pressure sensor connector wire insulation .
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