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The PCM is what grounds signal wire so this either means PCM has failed or blue/pink wire that goes between PCM and relay is broken. Disconnect PCM and ground the blue/pink wire at pin 17 of connector 2, if fan comes on replace the PCM. If fan does not come on run a new wire between relay and PCM. Let me know if you have more questions or if there is anything else I can do to help. Thanks.
No, the PCM activates the relay with ground. The gray wire should have battery voltage and black wire should have constant ground. Let me know if you have more questions, thanks.
You are right on everything other then blue/pink wire. The PCM provides blue/pink wire ground which activates the relay, not power like you thought. Let me know if you have more questions, thanks.
No there should not be voltage on that wire at any time. Let me know if you have more questions, at this point I'd do the above test to determine if problem is wiring or PCM. Keep me updated, thanks.