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 71, A/C Temperature (Circuit Open Or Shorted): Notes
The A/C system uses an A/C evaporator temperature sensor mounted in the A/C evaporator core to monitor A/C temperature for use by the PCM. The PCM uses this information to cycle the A/C compressor clutch so optimum cooling is attained. This will also prevent evaporator core freezing. The PCM will disable the A/C compressor clutch when A/C evaporator temperature is less than 36°F (2°C). A Code 71 will set under improper operating conditions; however, SERVICE ENGINE SOON light will not illuminate.
- Code 71 will set if A/C is requested and the PCM detects an open, short to ground or short to voltage in the evaporator temperature sensor circuit. All conditions must be met for 3 seconds for code to be set.
- With A/C evaporator sensor disconnected, normal voltage on circuit is near 5 volts. If a short to voltage is suspected, reconnect sensor harness and backprobe terminal "B" of sensor harness using a DVOM. If 5 volts or more is indicated, circuit is shorted to voltage.
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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.