What Does P0538 Mean?
The A/C evaporator temperature sensor is reporting a voltage signal above the expected range, indicating a high circuit condition. For NTC sensors, high voltage corresponds to an implausibly low temperature reading (or an open circuit). The PCM may disable the A/C compressor to prevent potential freeze damage, leaving the driver without cold air.
Common Causes
35%
Open circuit in the evaporator temperature sensor (sensor failed open internally)
30%
Broken or disconnected wiring in the sensor signal circuit
20%
Corroded, spread, or backed-out pins in the sensor connector
15%
Short to voltage (5V reference or battery) in the signal wire
Diagnostic Steps
1
Check the evaporator temperature PID — if it reads an implausibly cold value (e.g., -40°F) or maximum negative, the sensor circuit is open or shorted high.
2
Disconnect the sensor and measure resistance — an open reading (OL on the meter) confirms sensor failure; a normal reading of 10K-15K ohms at 77°F (25°C) points to a wiring issue.
3
With the sensor disconnected, use a jumper wire to briefly short the signal and ground pins at the harness-side connector — the scan tool reading should jump to a very high temperature, confirming continuity back to the module.
4
Inspect the connector pins for corrosion, spread terminals, or backed-out pins — the sensor connector behind the dash is often in a high-moisture environment from evaporator condensation.
5
Trace the wiring from the sensor to the HVAC module or PCM, checking for opens caused by rodent damage, dashboard work, or cabin filter replacement that may have disturbed the harness.
Estimated Repair Cost
$80 - $350
Parts + labor, varies by vehicle and location
The A/C evaporator temperature sensor is reporting a voltage signal above the expected range, indicating a high circuit condition. For NTC sensors, high voltage corresponds to an implausibly low temperature reading (or an open circuit). The PCM may disable the A/C compressor to prevent potential fre...
The most common cause of P0538 (A/C Evaporator Temperature Sensor Circuit High) is: Open circuit in the evaporator temperature sensor (sensor failed open internally)
Typical repair costs for P0538 range from $80 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. The PCM will likely disable the A/C compressor as a freeze-protection measure, leaving the cabin without cold air. No safety or drivetrain systems are affected.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0538 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
A/C & Climate Control
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
