On the 2001 Chevy Astro, the P0118 is a fairly straight forward code pointing to a fault with the Engine Coolant Temp (ECT) Sensor. Carefully inspect the electrical connector and wire harness for any loose, broken damaged or rubbed-through wires. If the visual inspection checks ok, suspect a faulty ECT Sensor. You can find the ECT Sensor mounted to the driver’s side cylinder head.
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