P0185 indicates a problem with the Fuel Temperature Sensor B circuit, meaning the powertrain control module has detected an out-of-range, irrational, or failed signal from the second fuel temperature sensor. The sensor reports fuel temperature so the engine controller can adjust fuel density and injection calculations; when the signal is unreliable, the code is set and the MIL turns on.
The thermistor or sensing element inside the sensor can drift out of range or fail entirely, producing an implausible voltage signal. This is the single most common cause of P0185.
Corroded, loose, bent-pin, or moisture-intruded connectors, plus chafed or broken wires, can create an open, short, or intermittent signal. This is the next most frequent cause after the sensor itself.
If the 5 V reference or sensor ground circuit is compromised by a poor connection or short to power/ground, the PCM will see an invalid fuel temperature signal and set the code.
Fuel contamination, debris, or damage from a prior repair can alter the sensor’s response or cause the sensor to read incorrectly. Ensuring correct installation torque and location matters.
A failed internal PCM input circuit is possible but uncommon. It should only be suspected after the sensor, connector, and entire wiring harness have been verified as good.
The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:
Usually not. The vast majority of P0185 cases are caused by the sensor, its connector, or the wiring. PCM replacement is rare and should only be considered after the sensor and all circuits are proven good.
Short trips are generally okay because many vehicles show no drivability symptoms, but the MIL will be on and emissions systems that rely on fuel temperature may not operate correctly. Have it diagnosed to avoid worsening wiring damage.
No. The B designation refers to a second fuel temperature sensor circuit, often located elsewhere in the fuel system. It has its own connector, wiring, and signal circuit.
It can contribute to incorrect fuel density or timing calculations, particularly on diesel or direct-injection engines, but many vehicles show only the check engine light with no drivability issues.