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.
Code 14B - Cts Circuit (Low Temperature Indicated): Notes
Coolant temperature sensor controls signal voltage to the ECM. The ECM applies voltage on circuit No. D12 to the sensor. When engine is cold, sensor resistance is high and ECM will see a high signal voltage. As engine warms, sensor resistance decreases and ECM will see a low signal voltage. When engine reaches normal operating temperature, signal voltage will be approximately 1.5-2.0 volts at the ECM. Coolant temperature is one of the inputs used to control fuel delivery, Electronic Spark Timing (EST) and Idle Air Control (IAC).
- Code 14B will set if engine has been running at least 3 minutes and coolant temperature is less than -31°F (-37°C) for 3 seconds.
- This simulates a Code 14A. If ECM recognizes low signal voltage (high temperature), ECM and wiring are okay.
- This determines if circuit No. A11 is open. Scan tester should display high temperature.
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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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