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P0185 OBD-II Trouble Code: Fuel Temperature Sensor "B" Circuit Malfunction

Check Engine Light

P0185 trouble code definition

Fuel Temperature Sensor “B” Circuit Malfunction

What the P0185 code means

  • P0185 is a OBD-II generic code indicating the fuel temperature sensor B is malfunctioning. The sensor is not within specification or the fuel temperature or fuel rail is too high or too low.

What causes the P0185 code?

  • The engine control module (ECM) sees that the sensor circuit is malfunctioning below or above the specified range designed for the sensor.

  • The code could be set if the fuel is too hot or too cold.

  • The fuel tank or fuel rail temperature sensor is out of sensor range or the connector is corroded.

  • The ECM monitors the temperature of the diesel fuel when the fuel heater is activated. If the temperature is out of range, it will turn on the Check Engine Light and set the code.

What are the symptoms of the P0185 code?

  • The vehicle will not start if the fuel is frozen from extreme cold conditions and water in the fuel.

  • If the fuel is too hot and is boiling, then the vehicle will not start, may stall, or loose power.

  • Excessive additives in the fuel can cause erratic sensor readings and cause the fuel to boil off at lower temperatures which would cause the sensor to malfunction.

  • The ECM sets code P0185 and turns on the Check Engine Light.

How does a mechanic diagnose the P0185 code?

  • Scans codes and documents the freeze frame data then clears the codes to verify if it returns

  • Performs a visual check of all the wiring and connections to the sensor to check for breaks in the wiring or loose connections

  • Disconnects connection to the sensor and checks to see if the sensor is testing within specifications.

  • Takes a fuel sample to compare temperature of fuel to the sensor input

  • Tests the diesel fuel heater for proper operation to make sure it is working to heat the fuel without overheating the fuel

Common mistakes when diagnosing the P0185 code

  • Not doing a visual check of connections to the sensor to make sure they are making good contact to the fuel heater and fuel temperature sensor.

  • Not checking the fuel for excessive additives that can cause sensors to malfunction.

How serious is the P0185 code?

  • The vehicle will not start If it has excessive amounts of water in the fuel, below freezing ambient temperature, and a defective fuel heater due to the temperature sensor.

  • The engine may misfire, hesitate, and stall if the fuel temperature exceeds normal operating temperature. This is a result of the temperature sensor circuit malfunctioning or the fuel rail getting too hot.

What repairs can fix the P0185 code?

  • Testing the fuel temperature sensor and replacing it if it is out of specifications

  • Repairing or replacing a defective connector or wiring to the sensor

  • Replacing the diesel fuel heater assembly with the temperature sensor

Additional comments for consideration regarding the P0185 code

The code P0185 is used on vehicles that have two fuel temperature sensors. Code P0180 is for sensor A and P0185 is for sensor B. Follow the manufacturer's recommended testing procedures for the vehicle and type of fuel you are working on.

Need help with a P0185 code?

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The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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