P0538 code meaning
A/C Evaporator Temperature Sensor Circuit High
What P0538 means
The evaporator temperature sensor, an NTC thermistor behind the evaporator, prevents icing: near 0–3 °C the compressor is switched off or reduced. Usually the climate module reads it and reports body codes; P0535–P0539 only arise where the engine module controls the compressor and reads the sensor. P0538 means the signal voltage is above its limit – an open sensor, signal or ground line, or a short to positive; with an NTC that reads as implausibly cold, so the system assumes icing and usually locks out the compressor. No manufacturer document available to us uses this code; the description follows CARB's input component rules.
P0538 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0538
- Air conditioning not cooling (compressor locked out)
- Vents blowing warm
- Usually no check engine light
Common causes of P0538
- Most likelyConnector off or corroded, wire open
- Most likelySensor open internally
- PossibleGround line open
- Less likelyShort to positive
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Evaporator temperature sensorSensor wiringEngine control module
What each part of P0538 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 38 | The exact fault in that area. |
What to do next
- Note P0538 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0538
What does P0538 mean?
P0538 means "A/C Evaporator Temperature Sensor Circuit High". The evaporator temperature sensor, an NTC thermistor behind the evaporator, prevents icing: near 0–3 °C the compressor is switched off or reduced. It is a generic code, so it means the same on every make.
Is it safe to drive with P0538?
P0538 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0538 fail an emissions test?
P0538 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0538 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0538 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.