Download 1999 Saturn SL1 L4-1.9L SOHC VIN 8 Vehicle Level Powertrain Management Computers and Control Systems Coolant Temperature Sensor/Switch (For Computer) Technical Service Bulletins All Technical Service Bulletins Engine – Driveability Concerns/Cooling System DTC’s Set. 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. ^If terminals are not corroded and there is no evidence of engine coolant, reconnect the electrical connector and continue to next step. 2. Perform one or both of the following checks to determine whether the engine coolant temperature sensor is providing the correct temperature indication. If engine coolant temperature sensor reading does not pass either of the above tests, continue with next step. ^If engine is at ambient temperature (vehicle has been sitting overnight or not started for several hours), use a Scan tool to compare the inlet air temperature ( IAT ) to the engine coolant temperature ( ECT ). These two readings should be within 2°C (4°F) of each other. ^If engine is at operating temperature, install a thermometer in the coolant recovery reservoir. With the engine running and A/C off, use a Scan tool to compare the engine coolant temperature sensor reading to the thermometer reading. These two readings should be within 8°C (15°F) of each other.
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