Code Definition

B1387 — Oil Temperature Sensor Circuit Open

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

About B1387

B1387 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 B1387 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit; and a sensor-related fault — the reported value from the named sensor is out of spec.

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.

B1387 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 monitors the oil temperature sensor circuit by supplying a 5V reference voltage to the sensor and measuring the resulting signal voltage as it drops across the sensor's thermistor element. DTC B1387 is set when the module detects an open circuit on this circuit, indicated by signal voltage staying at or near the reference value because no current is flowing through the sensor element. The oil temperature sensor uses a negative temperature coefficient thermistor whose resistance falls as oil temperature rises, allowing the module to calculate temperature for use by the g...

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