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Message: <blockquote data-quote="MultiVAC" data-source="post: 22124" data-attributes="member: 11910">Ran into an issue with my ECT sensor.  It and the PCM seem to use two different voltage ranges, from 2.5V(50deg F) to 1.0V (120F) then at 120F+ it starts back at 3.7V then decreases as temperature rises.  This causes the controllers, which expect a linear decrease across the whole range, to believe the engine is overheating until the sensor switches to the second range.  Fine for normal operating temps, but both fans ramp to 100%, pulling some 100A prior to reaching 120F which explains the dip in charge voltage at idle I was seeing.It sounds like a bad sensor, except the gauge, and OBD both display an appropriate calculated ECT across the whole range.  To verify I measured ECT sensor voltage across a warm-up.  Then I unplugged the sensor and measured ohms across a cool-down.  The voltage has the big spike, but the ohms do not, so the sensor is fine...  the PCM is probably using two different pullup resistors?  Not sure.To work around this I've ordered a second OEM ECT sensor and 680ohm pullup resistor to put in the driver-side cylinder head, plan is to feed it a reference 5V from the controller, then do a relearn procedure on the controllers.</blockquote>