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DTC codes / P01xx · Fuel and air metering / P0185

P0185Fuel Temperature Sensor B Circuit

P0185 indicates that the powertrain control module (PCM) has detected an abnormal voltage signal from the fuel temperature sensor B circuit, which is used to monitor the temperature of the fuel. The PCM expects the sensor's signal to stay within a specific voltage range, and when the reading falls outside that range for a set period, the code is stored.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp).
  • Often no symptoms besides the warning light, especially if the sensor fails gradually.
  • Possible rough idle or hesitation during cold starts if the PCM relies on fuel temperature for enrichment.
  • Slightly reduced fuel economy or poor driveability under certain conditions.
  • In rare cases, the engine may enter limp mode or exhibit hard starting.

Common causes, most likely first

  1. Faulty fuel temperature sensor B itself, such as an open or shorted internal element.
  2. Damaged or corroded wiring harness or connector at the sensor.
  3. Open or short circuit in the sensor signal circuit.
  4. Poor ground connection for the sensor circuit.
  5. PCM internal fault affecting the sensor reference voltage or signal processing.
  6. Contamination or degradation of the sensor due to fuel quality or age.

How to diagnose and fix it

  1. Use an OBD-II scanner to verify the code and check live data for the fuel temperature sensor B reading.
  2. Visually inspect the sensor and its connector for damage, corrosion, or loose pins.
  3. Measure the sensor's resistance with a multimeter and compare to the manufacturer's specification.
  4. Check the signal circuit for continuity and shorts to ground or power.
  5. Verify the reference voltage and ground at the sensor connector with the key on.
  6. If the sensor is faulty, replace it and clear the code.
  7. If the circuit is faulty, repair the wiring or connector as needed and re-test.

Fuel temperature sensor B circuit quirks

  • A common misdiagnosis is replacing the sensor when the real problem is a chafed wire in the harness, so always check circuit integrity first.
  • Fuel temperature sensor B is often integrated into a combined sensor assembly, and replacing just the temperature element may not be possible.
  • The PCM may use fuel temperature to adjust injection timing and EGR, so a faulty signal can affect emissions and performance without obvious symptoms.
  • In some vehicles, the fuel temperature sensor shares a reference voltage with other sensors, so a short in one circuit can set multiple codes.
  • Intermittent faults can be caused by vibration or heat, so wiggle-test the harness while monitoring live data.

Can I keep driving with P0185?

The vehicle is generally safe to drive with this code because it rarely causes immediate drivability issues, but avoid heavy loading or towing until repaired, as fuel temperature affects combustion efficiency. Have the fault diagnosed soon to prevent potential secondary issues.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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