Download SUBJECT: Engine Coolant Temperature Sensor Related Diagnostic Trouble Code(s) and/or the Following Conditions: Hard Start, Erratic Idle, Rough Running. Engine Overheating, Low and/or Leaking Coolant, and/or Service Engine Soon Lamp Illuminated. (Replace Engine Coolant Temperature Sensor with New Design Sensor- P/N 21025106) MODELS AFFECTED: 1991-2001 Saturn S-Series vehicles CONDITION: Customers may comment about various driveability and/or engine operating concerns including: hard start, erratic idle, rough running, engine overheating, low and/or leaking coolant, and/or Service Engine Soon lamp illuminated. CAUSE: This condition may be caused by a cracked engine coolant temperature sensor. CORRECTION: Replace engine coolant temperature sensor, inspect and if necessary replace sensor harness connector. Refer to procedure in this bulletin to replace engine coolant temperature sensor and Parts Requirements for specific parts information. PROCEDURE 1. Disconnect engine coolant temperature sensor electrical connector and inspect sensor and connector terminals for corrosion and/or evidence of engine coolant. ^ If terminals are corroded or if there is evidence of engine coolant proceed to step 4.