Powertrain, generic · Vehicle speed, idle control and auxiliary inputs
P0539 A/C Evaporator Temperature Sensor Circuit Intermittent
Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo
The evaporator temperature sensor, an NTC thermistor behind the evaporator, prevents icing: near 0–3 °C the compressor is switched off or reduced. Usually the climate module reads it and reports body codes; P0535–P0539 only arise where the engine module controls the compressor and reads the sensor. P0539 means short dropouts or jumps in the signal that do not add up to a lasting low or high fault – usually a loose contact or condensate corrosion at the connector; the compressor may switch off at times. No manufacturer document available to us uses this code; the description follows CARB's input component rules.
Likely causes
Loose contact or corrosion at the connector
Broken wire from movement or chafing
Sensor with internal intermittent contact
Symptoms
- Air conditioning failing at times
- Cooling fluctuates
- Usually no check engine light
Repair estimate
DifficultyMediumDIY possible
Parts and labour€20–400
Time0.5–4 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
evaporator temperature sensorsensor wiringengine control module
Related codes
References: hella.com, law.cornell.edu.