What Does P1438 Mean?
The A/C evaporator air temperature sensor signal is outside the expected range or not performing correctly compared to other temperature inputs. The reading may be implausible when compared to ambient or intake air temperatures during normal operation.
Common Causes
35%
Degraded or failing evaporator temperature sensor with drift
25%
Intermittent connection at sensor connector
20%
High resistance in sensor circuit wiring
12%
Sensor contaminated with debris or moisture affecting response
8%
Poor sensor ground connection
Diagnostic Steps
1
Step 1: Compare evaporator temperature reading with ambient and intake air temperature sensors on scan tool
2
Step 2: Monitor evaporator temperature data during A/C operation and verify sensor responds logically
3
Step 3: Inspect evaporator temperature sensor location for debris, moisture, or physical damage
4
Step 4: Check sensor connector and terminals for corrosion or poor contact
5
Step 5: Test sensor resistance at various temperatures and compare to manufacturer specifications
Estimated Repair Cost
$100 - $325
Parts + labor, varies by vehicle and location
The A/C evaporator air temperature sensor signal is outside the expected range or not performing correctly compared to other temperature inputs. The reading may be implausible when compared to ambient or intake air temperatures during normal operation.
The most common cause of P1438 (A/C Evaporator Air Temperature Circuit Range/Performance) is: Degraded or failing evaporator temperature sensor with drift
Typical repair costs for P1438 range from $100 to $325, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to operate. A/C system may cycle frequently, perform poorly, or disable to protect against evaporator freeze-up.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1438 to identify the root cause.
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Quick Info
Category
Powertrain
System
Climate Control System
Difficulty
Type
Manufacturer
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