More data:
Moved the resonator and got better access to the engine coolant temp (ECT) sensor, ohmmeter still telling me open circuit in the sensor. Haynes predicts 35-40 kohms.
Pulled the ECT sensor connector off, turned engine on. Like Fave said, CEL, but it was the HIGH-speed fan running. Plugged the ECT connector back in, fan kicked down to low speed for a couple mins then turned off. Engine was cold.
I'm confused - if the sensor is shot and shows open circuit always... how does the computer know if the connector is plugged in or not?
Further finding: cracked insulation on both ECT wires where they enter the connector. Perhaps this has shorted out and damaged the computer circuitry that reads the sensor? Hope not but looks like I'm overdue for a wiring harness replacement. Still haven't bothered to call Ford on that yet (115000 miles oops).
Will replace ECT ASAP and report.
