On the 2006 Chevy Equinox, the P0128 is a fairly straight forward code pointing to a fault with the Engine Coolant Temp (ECT) Sensor. Make sure the Coolant Level is full. Make sure there are no leaks in the Cooling System. Inspect the electrical connector and wire harness for any loose, broken or damaged wires. If the visual inspection checks ok, most commonly, replacing the ECT will solve the problem.
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