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

(6,114)

Rating Summary
5,655
221
51
35
152
5,655
221
51
35
152

Kevin

24 years of experience
388 reviews
Kevin
24 years of experience
Chevrolet Tracker - Check Engine Light is on - Stone Mountain, Georgia
Kevin was pretty cool! He explained things to me in a way I could understand and was able to offer me some good options to fix my car problems! Very professional and knew his stuff! Excellent experience

JOHNNY

33 years of experience
63 reviews
JOHNNY
33 years of experience
Toyota Camry - Check Engine Light is on - Carmichael, California
Johnny was early, friendly, and thorough! He explained things to me about my car that I had no idea about before! I booked him for a diagnostic appointment and I’m definitely requesting him for a follow-up!

Benji

22 years of experience
184 reviews
Benji
22 years of experience
Jaguar XK - Check Engine Light is on - Phoenix, Arizona
Will absolutely recommend Benjie to all my friends, thorough and knowledgeable. Will have him back fit all future car repairs!

Marco

29 years of experience
124 reviews
Marco
29 years of experience
Kia Soul - Check Engine Light is on - Riverside, California
Marco was great. Cam on time, and explained everything he did. Also gave good recommendation for fixing as the problem has a Kia recall.


More related articles

P0787 OBD-II Trouble Code: Shift/Timing Solenoid Low
P0787 means there is a problem with the shift/timing solenoid which may cause the transmission to not shift out of gear or have harsh shifting.
B1812 OBD-II Trouble Code: Lamp Backup Switch Input Circuit Short to Battery
B1812 means there is a circuit issue with a lamp backup switch, possibly due to a blown fuse or bulb defect.
P0358 OBD-II Trouble Code: Ignition Coil H Primary/Secondary Circuit Malfunction
Trouble code P0358 means the powertrain control module (PCM) has failed to receive a valid pulse signal from ignition coil H

Related questions

Fuel pump

This may happen when the fuel pump is working intermittently or not maintaining the proper fuel pressure. This may also be related partially to the fuel pressure regulator which helps to maintain the proper fuel pressure throughout the system. When...

Gas cap warning light stays on

I would take it back to the dealer that put the tank in and have them check their installation of the fuel tank. The lights should be off and no leaks detected with the new fuel tank. You may have...

My aura shakes when it starts saying "service traction" what is it?

Hello, thank you for writing in. At this point there are a lot of possible causes for your vehicle's symptoms. To gather more information, we need to start with having the vehicle scanned for diagnostic troubleshooting codes. This can be...

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