Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC 15, ECT Sensor Low Temperature Indicated (With A/ T): Notes
The Engine Coolant Temperature (ECT) sensor uses a thermistor which controls signal voltage from ECM. The ECM applies and monitors voltage over circuit No. 410 to sensor. When engine is cold, sensor resistance is high, the ECM will sense a high signal voltage. As engine warms, sensor resistance reduces and voltage drops. At normal engine operating temperature, voltage should be 1.5-2.0 volts. When DTC 15 sets, early application of torque converter clutch will occur.
- DTC 15 will set if signal voltage indicates a coolant temperature less than -27°F (-33°C) for 0.5 second.
- This test simulates DTC 14. If ECM recognizes low signal voltage (high temperature), and scan tester reads 145°C or greater, ECM and wiring are okay.
- This test determines if circuit No. 410 is open. Voltage at sensor connector should be 5 volts when measured with Digital Volt-Ohmmeter (DVOM).
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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