What are the best Buick repair shops?
RepairPal Certified shops can diagnose and repair your 1991 Buick Century. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
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Additionally OBD 1 trouble code 21 is related to the TPS (Throttle Position Sensor) / circuit.. The CTS (Coolant Temperature Sensor) trouble codes are 14 OR 15 .. Your question is about the “coolant temperature sender†would be temperature ‘gauge’ related. A professional scan test while the engine is COLD will make short work of diagnosis!