Code Definition

B1850 — Climate Control Temperature Differential Circuit Open

System: Body  |  Type: Manufacturer-Specific  |  Make: Generic

About B1850

B1850 is a manufacturer-specific body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1850 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

B1850 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The Body Control Module (BCM), or on some applications the Electronic Automatic Temperature Control (EATC) module, monitors the climate control temperature differential feedback signal to track blend door position and the actual cabin air temperature versus the commanded set point. DTC B1850 is set when the temperature differential signal circuit becomes open, meaning the module sees no return voltage on the feedback line from the sensor or actuator. This circuit typically uses a potentiometer or thermistor mounted in the HVAC housing, fed by a 5V reference, returning a voltage proportional to...

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