HVAC Post-Evaporator Temp Sensor Circuit
The HVAC control module has detected a fault in the post-evaporator temperature sensor circuit. This sensor monitors the air temperature after it passes through the evaporator to prevent ice formation and regulate compressor cycling. The code sets when the sensor signal is out of range (open circuit, short to ground, or short to battery) for a calibrated period.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty post-evaporator temperature sensor (open or internally shorted)
- Damaged, corroded, or shorted wiring or connectors in the sensor circuit
- Internal HVAC control module failure (rare)
3. Symptoms You Will Notice
- A/C system may blow warm air or fail to cool properly
- Compressor may cycle erratically or stay engaged continuously
- Possible ice buildup on evaporator causing reduced airflow
4. Step-by-Step Diagnosis
Scan for additional HVAC-related codes and note freeze frame data
Visually inspect the post-evaporator temperature sensor and its wiring for damage or corrosion
Measure sensor resistance and compare to specifications; check for open or short circuits
Test sensor signal voltage at the HVAC module connector with the sensor connected
If sensor and wiring are good, suspect a faulty HVAC control module
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but the A/C may not work properly. Continued driving with a faulty sensor can lead to evaporator icing or compressor damage, so it should be repaired soon.
How much does it cost to fix?▼
Typical repair costs range from $150 to $400, including parts and labor. The sensor itself is usually $30–$80, with labor adding $100–$200 depending on accessibility.