e4
Moderate
Trane · HVAC Systems (AC, Furnaces & Heat Pumps)
Sensor Fault
Quick Answer
Error code E4 on your Trane HVAC Systems (AC, Furnaces & Heat Pumps) means: Sensor Fault. This is usually fixable — see the step-by-step guide below.
Likely Causes
How to Fix It
1
Locate the outdoor temperature sensor and check the connector for corrosion or damage
2
Measure sensor resistance with a multimeter and compare to the manufacturer resistance-temperature chart
3
Check the wiring from the sensor to the outdoor control board for breaks or shorts
4
Replace the sensor if resistance readings are out of specification
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Outdoor temperature sensor (thermistor)
Wire connectors
Electrical tape
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