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Diagnostic Aids

Check vehicle wiring harness for a potential short to ground in circuit No. 410. After engine is started, the temperature should rise steadily to approximately 203°F (95°C) then level off when thermostat opens. Ensure engine is not overheating or has been subjected to conditions which will cause engine to run too hot such as trailer towing. Use the Coolant Temperature Sensor Temperature To Resistance Values table to diagnose a "shifted" sensor which could cause poor driveabilty. If code is intermittent, refer to TESTS W/O CODES article.

Fig 1: Code 15, Circuit Wiring Diagram & Flow Chart
G121691Courtesy of GENERAL MOTORS CORP.