Diagnostic Aids
After engine is started, the temperature should rise steadily to approximately 203°F (95°C) then level off when thermostat opens. If Codes 15 and 21 are stored at the same time, there could be an open in circuit No. 452. 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.