A/C Evaporator Temperature Sensor Circuit Low
The P0537 code indicates that the A/C evaporator temperature sensor circuit is reading a voltage lower than the expected range. This sensor monitors the temperature of the evaporator core to prevent freezing and control A/C operation. A low circuit voltage typically points to a short to ground, faulty sensor, or wiring issue.
1. Most Common Causes
- Faulty evaporator temperature sensor (internal failure)
- Sensor circuit shorted to ground
- Corroded, oxidized, or damaged sensor connector pins
- Excessive resistance in sensor circuit due to poor splices or connections
- Faulty HVAC control module or ECM/PCM (less common)
2. Symptoms You Will Notice
- A/C system not cooling properly
- A/C compressor cycling on and off rapidly
- A/C system may not engage at all
- Check Engine Light illuminated
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P0537 and check for related codes.
Step 2: Visually inspect the A/C evaporator temperature sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Disconnect the sensor and measure resistance; compare to manufacturer specs (typically 2-10 kΩ at 77°F).
Step 4: Check for voltage at the sensor connector (should be around 5V reference). If low, test for shorts to ground in the wiring.
Step 5: If sensor and wiring are okay, test the PCM for proper operation (rare).
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but the A/C may not work properly. Driving without A/C is safe, but if the sensor fails, it could cause the compressor to run continuously and freeze the evaporator, potentially damaging the system.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor. The sensor itself costs $20-$50, and labor is about $30-$100 depending on accessibility.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.