15 ECT Circuit - Temperature Out of Range Low
From SaturnWiki
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Description
The coolant temperature sensor (CTS) is a thermistor located in a coolant passage. When coolant temperature is cold the sensor has a high resistance, as temperature increases the resistance of the sensor decreases. The PCM provides a five volt signal to the coolant sensor, which is also connected to PCM ground. The PCM reads the voltage drop on the signal line to determine coolant temperature.
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Code Parameters
Code 15 will set if:
- The CTS reads below -35°C (-31°F).
- The engine has been running longer than five minutes with a temperature less than -35°C (-31°F).
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Diagnostic Aids
- Refer to Temperature vs. Resistance Chart.
- When attempting to diagnose an intermittent problem, use the Scan Tool to review supplemental diagnostic information.
- The supplemental data can be used to duplicate a problem. Select MALF History from Scan Tool EC menu.
- Check the tightness of the female terminal grip with a spare male terminal.
- Start engine and observe CTS reading on Scan Tool.
- Normal operation is for the CTS to rise smoothly to approx. 88°C (190°F) (thermostat opens) then stabilize.
- Visually inspect CTS wires for damage. Wiggle wires while observing scan tool CTS reading and watch for a sudden shift in temperature.
- CTS may be compared to ATS temperature, with a Scan Tool if engine has cooled overnight at ambient temperature. They should be within four degrees of each other with ignition On - engine Off
