P0538 OBD-II Trouble Code: A/C Evaporator Temperature Sensor Circuit High

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0538 code

P0538 is a diagnostic trouble code (DTC) for "A/C Evaporator Temperature Sensor Circuit High". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0538 DIAGNOSTIC Get a fair and transparent estimate upfront

P0538 A/C evaporator temperature sensor circuit high definition

A P0538 code indicates that the powertrain control module (PCM) has registered voltage readings from the A/C evaporator temperature sensor that are outside of norms, triggering a trouble code.

What the P0537 code means

The temperature switch in an automotive A/C system is mounted in the fins of the evaporator core and uses a capillary design. When the evaporator core’s temperature drops, the capillary pressure in the switch drops as well. This lowers circuit resistance and increases the voltage input signal to the powertrain control module (PCM). The PCM registers this as a change in temperature and begins to cycle the compressor clutch on and off. A trouble code is registered when these voltage fluctuations differ from the reference limit. Usually three failure cycles are necessary before the PCM will store a code and illuminate the Malfunction Indicator Lamp (MIL).

What causes a P0538 code?

  • Failed evaporator temp sensor
  • Failed expansion valve, resulting in freeze up of the evaporator core
  • Damaged or shorted wiring
  • Overcharged A/C system
  • Low refrigerant condition
  • Faulty climate control head unit

What are the symptoms of a P0538 code?

  • Inoperative A/C system
  • Stored code, illuminated MIL
  • Air conditioning “ON” indicator lamp (on A/C switch) flashes repeatedly
  • Freeze up of the evaporator case, with condensate dripping onto floor

How does a mechanic diagnose a P0538 code?

An OBD-II code reader/scanner, digital volt/ohmmeter and a set of A/C gauges or A/C recycling machine with built-in gauges will be needed for a proper diagnosis and repair.

  • Begin your diagnosis by visually inspecting all wiring and connectors. Repair/replace any damaged, disconnected, corroded or shorted wiring, connectors and parts as needed. Retest the system.

  • If all wiring, connectors, parts and fuses appear to be in good working order, connect the scanner/code reader to the diagnostic port. Record any stored codes and freeze frame data.

  • Test drive the vehicle and re-test to see if the code returns. If not, the problem may be an intermittent condition. Intermittent conditions can be a challenge to diagnose correctly and may need to be allowed to worsen and return before a proper diagnosis can be made.

  • Connect A/C gauges to the proper fittings, start the engine and turn the A/C blower on its highest setting, with A/C on Max. Observe gauge readings and compare to factory specs, adding refrigerant level as needed. Turn the blower speed to Low, then observe gauges for pressure readings.

  • If system’s low-side pressure falls too much – below 25 psi or so – it can cause a freeze up of the evaporator and a trouble code. If this occurs, the expansion valve could be at fault.

  • If the A/C system operates normally, perform a resistance test on the evaporator temperature sensor’s electrical connector (after unplugging the sensor)

  • Compare your findings to factory specs, replace sensor if needed.

  • If evaporator temperature sensor seems to be within operating norms, disconnect the PCM electrical connector and electrical connector for the climate control head unit. Perform a resistance/continuity test on the evaporator temperature sensor circuit. Repair/replace any shorted or open wiring if indicated. If the evaporator temperature sensor and circuits test as good, suspect the climate control head unit itself or the A/C compressor switch.

  • Test unit, compare to factory specs and replace components as needed.

Common mistakes while diagnosing P0538 code

Often, with a P0538 code, technicians or owners overcharge their vehicles’ systems with refrigerant, resulting in problems. It’s important to make certain that it’s absolutely necessary to add refrigerant before moving forward, and only qualified personnel with the right tools/equipment should attempt this service. Single hose charging kits, with no gauge or an inadequate gauge, are often a recipe for trouble.

How serious is a P0538 code?

Operating the A/C system with a P0538 code can lead to further problems and failure of other components.

What repairs can fix a P0538 code?

Addition comments for consideration for P0538 code

While the lines, O-rings and gaskets of an A/C system are porous and even a newer vehicle can lose 5 percent of its refrigerant over a year’s time, it’s important to not simply add refrigerant if a P0538 code is registered. Make sure you’ve found the root cause of the P0538 code before going any further. Note that the P0538 code indicates a high reading from the evaporator temperature sensor circuit, as opposed to the low reading of a P0537 code.

Need help with a P0538 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

trouble codes
P0538
Check Engine Light

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0538 code.

SCHEDULE P0538 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

5,170

Rating Summary
4,765
197
50
27
131
4,765
197
50
27
131

Fred

16 years of experience
364 reviews
Fred
16 years of experience
Mercedes-Benz E500 - Check Engine Light is on - Conroe, Texas
Fred was very friendly and thorough to get to the root of the issue. Even when he could not find a fault to why my engine light was on, he went above and beyond to make absolutely sure that the concern was minimized. Turns out, all that needed to be done was a reset but his diagnostic to address my issues was very intricate and appreciated.

David

17 years of experience
37 reviews
David
17 years of experience
Chevrolet Cruze - Check Engine Light is on - Aurora, Colorado
David was on time, professionalisms & honest! I would definitely request him again and pass along to friends/family.

John

18 years of experience
18 reviews
John
18 years of experience
Dodge Ram 1500 - Check Engine Light is on - Memphis, Tennessee
Demonstrated good integrity. Advised me when work I thought needed done was unnecessary and was helpful in identifying issues that needed to be addressed

Robert

21 years of experience
17 reviews
Robert
21 years of experience
Chrysler 200 - Check Engine Light is on - Fort Worth, Texas
Robert did a good job working on my car and letting me know what's needed to keep my car driving smoothly.


More related articles

P2646 OBD-II Trouble Code: 'A' Rocker Arm Actuator System Performance / Stuck Off Bank 1
P2646 code definition 'A' Rocker Arm Actuator System Performance or Stuck Off Bank 1 What the P2646 code means P2646 is an...
P0930 OBD-II Trouble Code: Gear Shift Lock Solenoid Circuit Low
P0930 means a problem with the shift lock solenoid which keeps the gear shifter from being moved out of park without the brake pedal pressed down.
How Long Does an EGR Temperature Sensor Last?
Are Are you familiar with the EGR (exhaust gas recirculation) system in your car? If not, this is something all modern cars have. The purpose of this system is to greatly reduce the amount of emissions produced by your car....

Related questions

I have,a 2005 mercury montego it has a code p0320 and p2106 where should I start first cam or crank

Hello, thank you for writing in. Due to the codes that you have currently, you will want to start with the crankshaft position sensor. You can test it with a multi-meter or voltmeter if you are equipped. If may be...

My Check Engine Light turns on and off, and the Service Traction Light is on

There are several components that can cause these types of symptoms. Issues that cause poor performance and shaking can be fuel, air, spark, electronic, or mechanical problems. The good news is that the Check Engine Light has come on. This...

P2118 where to look for the issue

Hello, thank you for writing in. You are throwing a code for the throttle body actuator control motor. More particularly, it means that the computer which monitors the throttle actuator has detected that the motor is working outside of it...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com