P0538
A/C Evaporator Temperature Sensor Circuit High
A/C & climate control
Generic OBD-II
Low
What it means
P0538 means the ECM or HVAC module sees an abnormally high voltage on the A/C evaporator temperature sensor circuit — usually an open circuit, a short to power, or a failing sensor. This sensor helps prevent the evaporator from freezing and controls compressor cycling, so a bad reading can weaken or disable cooling. It only affects the A/C, not how the engine runs.
Low
Can I keep driving? Safe to drive — only the air-conditioning is affected. The engine runs normally; you may just get weaker or inconsistent A/C cooling.
Common symptoms
What you'll notice
- Weak, inconsistent, or non-functioning A/C cooling
- A/C compressor may cycle oddly or stay off
- Check-engine or A/C warning light on
- Engine performance unaffected
Common causes
Most likely first
- Faulty A/C evaporator temperature sensorLikely
- Open circuit or short-to-power in the sensor wiring (high voltage)Common
- Corroded or loose connector at the sensorCommon
- Damaged wiring in the HVAC harnessLess often
- HVAC control module or ECM fault (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the code with a scan tool.
- Locate the evaporator temperature sensor and inspect its connector and wiring.
- Check for an open circuit or short to power causing the high reading.
- Compare the sensor resistance/voltage against spec at a known temperature.
- Replace the sensor if it reads out of range. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0538?+
Yes. It only affects the A/C system; the engine runs normally. Fix it if you want reliable cooling and to clear the light.
Can I just clear P0538?+
It returns until the sensor or its wiring is repaired. Clearing only resets the light.
Related codes
Often seen with P0538
Read & clear P0538 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX