Evaporator Temperature Sensor Circuit High
The P0538 code means the vehicle's onboard diagnostic system has detected: Evaporator Temperature Sensor Circuit High. This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- hard
- Estimated cost
- $100 - $500 (parts and labor)
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What Are the Symptoms of P0538?
- Check Engine Light on
- Evaporator may freeze up
- AC runs constantly without cycling
- Ice buildup on evaporator
What Causes P0538? (Most Likely First)
- Open circuit in evaporator temperature sensor wiring Very High
- Failed sensor with open internal circuit High
- Disconnected evaporator temperature sensor connector Moderate
- Corroded pins causing high resistance in sensor circuit Moderate
Can I Still Drive with P0538?
Yes, but fix soon. P0538 is rated low severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring the light.
Frequently Asked Questions
Why does the evaporator freeze with P0538?
When the sensor reads high (falsely indicating a warm evaporator), the system never cycles the compressor off to prevent freezing. The compressor runs continuously, dropping the evaporator temperature below freezing and causing ice buildup.
How do I know if my evaporator is frozen?
A frozen evaporator blocks airflow through the vents. You may notice reduced or no airflow from the vents even with the blower on high, followed by a gush of water when the ice melts after shutting off the AC.
What does circuit high mean for P0538?
Circuit high means the sensor signal voltage is above the expected maximum, making the system read an extremely warm temperature. This is typically caused by an open circuit (broken wire or disconnected sensor) where the pull-up voltage reads through.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P0538?
-
Read evaporator temperature sensor value; an extremely warm reading when AC is running cold confirms circuit high
-
Check sensor connector for disconnection or corrosion
-
Measure sensor resistance; an open reading (infinite ohms) confirms sensor failure
-
Inspect wiring for breaks, especially where it passes through the firewall or HVAC housing
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Which Vehicles Commonly Get P0538?
- 2010-2020 Ford Explorer
- 2012-2019 Chevrolet Silverado
- 2008-2018 Toyota 4Runner
- 2011-2020 Honda Pilot
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