P0537
A/C Evaporator Temperature Sensor Circuit Low.
- Generic
- Powertrain
- Generic code
- Low severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 37
- FaultThe specific fault in that area
What it means
P0537 means the control unit has seen the A/C evaporator temperature sensor signal voltage fall below the expected range. The sensor is a thermistor that tells the system how cold the evaporator is so it can stop the compressor before the coil freezes. A low voltage reading usually points to a short to ground in the circuit or a failed sensor.
Symptoms
- A/C blows warm or does not get as cold as usual
- A/C compressor will not engage or cycles on and off erratically
- A/C compressor stays off to protect the system
- Evaporator may ice up if the compressor runs without proper control
- Warning light on, or A/C control panel behaving oddly on some models
Possible causes
- Failed evaporator temperature sensor with an internal shortlikely
- Signal wire chafed and shorted to groundlikely
- Water ingress, corrosion or damage at the sensor connectorpossible
- Sensor signal wire shorted to the sensor ground or another ground circuit within the harnesspossible
- Faulty climate control module or powertrain control module input circuitrare
- Incorrect or non-matching sensor fitted after a previous repairrare
How to diagnose
- Read all stored codes and freeze frame data, and note whether the fault is current or intermittent
- Check the live data for evaporator temperature and compare it with the cabin air temperature and the vent temperature; a reading stuck at an extreme cold value suggests a short
- Visually inspect the sensor, its connector and the harness for chafing, corrosion, moisture or damage
- Unplug the sensor and check the live data again; if the reading changes to an open-circuit value, the sensor is likely at fault
- Measure the sensor resistance and compare it with the manufacturer's specification at a known temperature
- Check the signal wire for a short to ground between the sensor and the control unit with the connectors disconnected
- Check the reference voltage and ground supply at the sensor connector against the wiring diagram for your model
- If wiring and sensor are good, test the control unit input following the manufacturer's procedure
How to fix
- Replace the evaporator temperature sensor with the correct type for the vehicle
- Repair or replace the damaged wiring where the signal wire is shorted to ground
- Clean or replace corroded connectors and terminals, and seal against moisture
- Replace the faulty control unit only after the wiring and sensor have been proven good
- Clear the code after repair and confirm that the A/C operates normally and the code does not return
Can I keep driving?
Low severity
The car is safe to drive, as this fault mainly affects A/C operation. Book it in at your convenience, and avoid running the A/C if it behaves oddly, to prevent evaporator icing.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.