AutoCodes – Generic – P0538

P0538 Code - A/C Evaporator Temperature Circuit High Input

Quick Answer

The A/C Evaporator Temperature (ACET) sensor contains a thermistor which receives a reference voltage from the Powertrain Control Module (PCM). Common causes include Faulty A/C Evaporator Temperature (ACET) Sensor, A/C Evaporator Temperature Sensor harness is open or shorted, A/C Evaporator Temperature Sensor circuit poor electrical connection. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: P0538 indicates A/C Evaporator Temperature Circuit High Input.
Common causes: Common causes include Faulty A/C Evaporator Temperature (ACET) Sensor, A/C Evaporator Temperature Sensor harness is open or shorted, A/C Evaporator Temperature Sensor circuit poor electrical connection.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 18,823

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 28, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P0538 Description

The A/C Evaporator Temperature (ACET) sensor contains a thermistor which receives a reference voltage from the Powertrain Control Module (PCM). The thermistor then varies the resistance to the reference voltage based on the evaporator discharge air temperature. The resulting voltage is returned to the PCM where it is interpreted as an evaporator discharge air temperature reading.
The PCM maintains evaporator core temperature and prevents icing of the evaporator core, by disengaging the A/C compressor clutch (non-hybrid) or decreasing the electric A/C compressor speed (hybrid) when the evaporator A/C Evaporator Temperature sensor reading falls below acceptable levels, and by engaging the A/C compressor clutch (non-hybrid) or increasing the electric A/C compressor speed (hybrid) when the discharge air temperature rises above acceptable levels.
The A/C Evaporator Temperature sensor is located inside of the heater core and evaporator core housing in the air-stream leaving the evaporator core.
The Diagnostic Trouble Code (DTC) indicates the A/C Evaporator Temperature sensor signal input is not to factory specifications.

OBDII Code P0538 - A/C Evaporator Temperature Circuit High Input - AutoCodes.com — P0538 Code - A/C Evaporator Temperature Circuit High Input

What does this mean?

What are the Possible Causes of the DTC P0538?

Faulty A/C Evaporator Temperature (ACET) Sensor
A/C Evaporator Temperature Sensor harness is open or shorted
A/C Evaporator Temperature Sensor circuit poor electrical connection
Faulty Powertrain Control Module (PCM)

How to Fix the DTC P0538?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0538 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0538 code?

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Need Help with the Code?

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Information for Specific Makes

P0538 Ford — A/C Evaporator Temperature Circuit High Input
P0538 Lincoln — A/C Evaporator Temperature Circuit High Input
P0538 Mercury — A/C Evaporator Temperature Circuit High Input

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.