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 P073, Intermittent Engine Coolant Temp Sensor Signal: Notes
Engine Coolant Temperature (ECT) sensor circuit uses 2 pull-up resistors for temperature sensing. When sensor resistance is high (indicating low temperatures), PCM uses 3.65-k/ohm resistor and 348-ohm resistor in series. As temperature increases to 122°F (50°C), sensor resistance will decrease to 973 ohms. This resistance corresponds to .97 volt at PCM. At this point PCM shifts to single 348-ohm pull-up resistor to measure temperature greater than 122°F (50°C).
PCM monitors voltage signal of circuit and assumes engine operation causes coolant temperatures to change at slow rates. This test monitors ECT sensor voltage. If PCM detects a large change in sensor output voltage in a one-second period, code will set.
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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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