On the 2003 Cadillac Seville, If the coolant level in the reservoir is correct and the warning message still appears, this will be a problem with the Coolant Level Sensor. The sensor is built into and part of the Coolant reservoir. Inspect the electrical connector and wire harness for any loose, broken or damaged wires. If the inspection checks ok, the Coolant reservoir will need to be replaced. To gain access to the reservoir, the air filter housing will first need to be removed.
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