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Just going to copy/paste myself from a previous post lol. Do you get bulb checks (WTS, WIF, etc?) when you turn the key on?

If the alternator wasn't charging but you get a GEN light on the dash -- alternator bad.
No tach, no charging, but speedo works -- ESS issue.
Tach+charging, no speedo -- VSS issue.
No tach, no charging, no speedo, no bulb checks -- PCM is bad (Maybe not fried, maybe just power/ground issues)
 
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Intriguing. Yeah, I think if the ESS had failed in such a way it was shorting the 5V supply to ground, it might cause the PCM not to boot. That's not a typical failure case for a solid-state part like that, but I guess nothing's impossible. Would suggest checking the pins at the ESS connector for continuity to chassis ground first (The ESS harness has a couple places it might rub, especially if a PO or mechanic did not route it properly), but seems like replacing the ESS is the way to go.
 
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