B1859: Climate Control A/C Pressure Switch Circuit Open
MediumBodyClimate Control
What does B1859 mean?
B1859 is a diagnostic trouble code indicating "Climate Control A/C Pressure Switch Circuit Open". This means there is an electrical break in the climate control wiring — a connector may be unplugged, a wire broken, or a component has failed internally. The ECU detected no signal where it expected one.
Common causes
- Damaged or corroded wiring harness
- Loose or disconnected electrical connector
- Failed climate control sensor or actuator
- Blown fuse in the related circuit
- Poor ground connection
What should you do?
Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.
Get a diagnosis for YOUR car
Code B1859 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.