What does it mean?
P1533 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: A/C Evaporative Temp Sensor Circuit High Input .
Symptoms
- Check engine light on with poor or absent cooling from the air conditioning
- Compressor not engaging at all, or cycling on and off very quickly
- Vent air only slightly cool even with the system set to maximum
- Evaporator icing up in some cases, with a drop in airflow
- Air conditioning working intermittently, better on some days than others
- Engine performance unaffected
Likely causes
- Open circuit in the sensor signal or ground wire
- Sensor internally open or drifted to a very high resistance
- Corroded connector behind the dashboard or inside the evaporator housing
- Water leaking from the evaporator drain into the connector
- Sensor probe dislodged from the evaporator fins, so it never sees the real temperature
- Broken wire where the harness passes through the heater box
- Module input circuit failure as the final possibility
How to fix it
- Read the evaporator temperature in live data and compare it with the actual ambient temperature
- Unplug the sensor and measure its resistance, then compare it with the temperature and resistance relationship for that sensor
- Bridge the sensor connector briefly; if the reading swings to the opposite extreme, the wiring is intact and the sensor is at fault
- Inspect the connector for moisture, corrosion and green terminals, especially near the evaporator drain
- Check the signal and ground wires for continuity back to the module
- Refit the probe correctly into the evaporator fins if it has come loose
- Replace the evaporator temperature sensor, then confirm the compressor cycles normally