P0537 A/C Evaporator Temperature Sensor Circuit Low

P0537 indicates a low signal from the A/C evaporator temperature sensor circuit. The controller sees evaporator temperature feedback below the expected electrical range.

Code details

Generic OBD-II · P0

System: Speed / Idle
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not bypass evaporator freeze protection until the low temperature signal is diagnosed.

Symptoms of P0537

Unstable, high, or low idle, or stalling.
Erratic speedometer, cruise-control, or shift behaviour.
Check-engine light with a hesitation or surge.

Common causes of P0537

A dirty throttle body, idle-control valve, or throttle-position sensor.
A failing vehicle-speed or wheel-speed sensor, or its wiring.
Vacuum leaks or a related sensor forcing the idle/speed strategy.

Useful checks before replacing parts

Check sensor signal voltage, reference voltage, ground, evaporator temperature reading, compressor command, freeze-frame data, and related low-input codes.
Inspect for short-to-ground faults, open reference circuits, connector moisture, damaged HVAC harness sections, and sensor internal failure.
Compare the scan-tool temperature to ambient and vent temperature to separate an electrical low signal from a true freeze-up condition.

Related OBD-II codes

These nearby speed / idle entries can help compare wording and pin down the fault area.