Skip the auto shop - Our mechanics make house calls

P0539 OBD-II Trouble Code: A/C Evaporator Temperature Sensor Circuit Intermittent

check engine light

P0539 code definition

When the Powertrain Control Module (PCM) detects a voltage reading from the A/C evaporator temperature sensor that lies outside of the specifications as set by the manufacturer, a P0539 trouble code is stored. Some additional related trouble codes include a P0535, P0536, P0537, and P0538 code.

What the P0539 code means

A variation of either too high or low in the voltage signal coming from the A/C evaporator temperature sensor causes the storage of a P0539 trouble code and the Check Engine light to illuminate.

What causes the P0539 code?

A faulty evaporator temperature sensor is usually the source of the storage of a P0539 trouble code. Some other reasons for the storage of the code include faulty electrical connections, damaged or shorted wiring, a faulty climate control head, a low refrigerant condition, an overcharged A/C system, or a faulty expansion valve causing the evaporator core to freeze up.

What are the symptoms of the P0539 code?

An inoperative A/C system is the most common symptom of a P0539 trouble code. Some other symptoms of this code include the A/C ON indicator flashing repeatedly or the evaporator case freezing up and dripping onto the floorboard of the vehicle.

How does a mechanic diagnose the P0539 code?

Diagnosing and repairing a P0539 trouble code requires a mechanic to have certain equipment, including an OBD-II scanner, digital volt/ohmmeter, and a set of air conditioning gauges. The mechanic should also perform the following when attempting to diagnose a P0539 trouble code:

  • Visually inspect all wiring, connectors, and components.
  • Connect the scanner to the diagnostic connector in order to download any stored trouble codes or freeze frame data. This information could come in handy with diagnosing the vehicle's problems, especially if the condition is intermittent.
  • Clear the P0539 trouble code and test the system.
  • If it returns, connect the A/C gauges to the proper fittings and turn the A/C on max and the blower on high. The mechanic should then compare any readings to the manufacturer's specifications.
  • Next, after adding the required amount of refrigerant, the mechanic should turn the blower speed to low and compare the readings to the manufacturer's specifications.
  • If the A/C system is operating normally, the mechanic should unplug the evaporator temperature sensor electrical connector and test the resistance of the sensor using the digital volt/ohmmeter.
  • Clear the P0539 trouble code and retest the system to see if the trouble code returns.

Common mistakes when diagnosing the P0539 code

A common mistake made by mechanics when trying to fix a P0539 trouble code is to assume it is caused by a low refrigerant condition. The refrigerant is then overfilled by the mechanic, causing a catastrophic failure. To avoid this, vehicle owners should only have a qualified mechanic, with the proper tools, service the A/C system in their vehicle.

How serious is the P0539 code?

Fortunately, a P0539 trouble code is not that serious, with the most likely symptom a non-working A/C system or, at most, a wet floorboard.

What repairs can fix the P0539 code?

Repairing a P0539 trouble code requires the mechanic to perform certain steps, including:

Additional comments for consideration regarding the P0539 code

If, after diagnosing the evaporator temperature sensor or any related circuitry, the mechanic fails to find the source of the problem, the mechanic should suspect a faulty A/C compressor switch or climate control head. The mechanic needs to perform subsequent testing of these components to see if the problem lies there.

Need help with a P0539 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222 code means The manufacturer specifies a range of acceptable voltage to be produced from the throttle position...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...


Related questions

Q: Engine came on and we took it to Autozone. Code read P0430

Hello. This issue can be caused by a failing catalytic converter or by a bad oxygen sensor. As for driving the vehicle, if it is not lacking any power then it should be fine to drive. The only time a...

Q: Service engine soon light is on can not turn it off

In order to get the check engine light to turn off is to get a check engine light inspection having a mechanic like one from YourMechanic come to you and scan the computer to retrieve the stored codes and diagnose...

Q: What Causes Leaks in a Car's AC System?

Automotive air conditioning (AC) is a closed loop system comprised of four main mechanical parts: the compressor, condenser, evaporator, and depending on system design, receiver drier or accumulator. Refrigerant is circulated through these components with the refrigerant pressure and temperature...