Code Definition

P0187 — Fuel Temperature Sensor B Circuit Low Input

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0187

P0187 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0187 is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0187 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Engine Control Module monitors fuel temperature using sensor B, a negative temperature coefficient thermistor supplied with a 5V reference through a pull up resistor inside the module. DTC P0187 sets when the ECM detects that the signal voltage on the sensor B circuit has fallen below the calibrated low threshold, typically under about 0.2V, for a defined period. Because the sensor is a negative temperature coefficient device its resistance falls as fuel temperature rises, so a low signal voltage is interpreted by the module as an implausibly high fuel temperature, which most commonly resu...

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