Escalade, Suburban 1500 & 2500, Tahoe, Yukon, Yukon XL 1500 & 2500 (2006-2007), Yukon Denali and Yukon Denali XL (2005-2006)
Remove the ECT sensor.
Measure and record the resistance of the ECT sensor at various temperatures, then compare those measurements to the following. The change in resistance should occur smoothly. If there are any sudden changes, the sensor is faulty.
If the sensor tests outside of these ranges, replace the sensor.