The code indicates that the voltage signal from fuel temperature sensor B is below the expected range, typically meaning the circuit is shorted to ground or the sensor has failed internally. The powertrain control module monitors this sensor to adjust fuel delivery calculations based on fuel density, which varies with temperature. When the voltage drops below calibrated limits for a set period, the diagnostic trouble code is stored and the malfunction indicator lamp illuminates.
The thermistor inside the sensor may have shorted internally or drifted out of specification, causing the resistance to drop and the signal voltage to fall below the PCM's calibrated threshold.
The wiring harness between the sensor and the PCM may have chafed against the frame, engine block, or exhaust heat shield, creating an unintended path to ground that pulls the circuit voltage low.
Moisture intrusion or oxidation inside the sensor connector can bridge the signal terminal to the ground terminal, effectively shorting the circuit and producing a low voltage reading.
If the 5-volt reference line shared with other sensors shorts to ground anywhere in the harness, it can cause the fuel temperature sensor circuit to register abnormally low voltage.
Although uncommon, an internal short within the PCM's analog-to-digital converter or input circuitry could incorrectly interpret a normal sensor signal as low voltage, but this should only be considered after wiring and sensor testing.
Generally yes for short distances, as this code primarily affects emissions calculations and long-term fuel trim adaptations rather than causing immediate mechanical damage, though you may notice minor performance changes.
Only if the temperature sensor is physically integrated into the fuel pump module and listed as non-serviceable by the manufacturer; many applications allow the sensor to be replaced independently of the pump.
It is uncommon; the vast majority of P0187 codes are resolved by replacing the sensor or repairing damaged wiring. PCM replacement should only be considered after exhaustively verifying wiring integrity and confirming the sensor operates correctly.
Sensor B typically refers to a secondary fuel temperature sensor, often located in the fuel rail or return line, whereas Sensor A usually refers to the primary sensor located in the fuel tank or integrated with the fuel pump assembly.