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 14A - Cts Circuit (High 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 14A will set if engine has been running for at least 3 minutes and signal voltage indicates a coolant temperature greater than 302°F (150°C).
- This simulates conditions for Code 14B. If ECM recognizes open circuit (high voltage), and displays low temperature, ECM and wiring are okay.
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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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