P0189 Fuel Temperature Sensor B Circuit High Input

As a car owner, it can be frustrating to have a check engine light come on.

One of the codes that might appear is P0189, which refers to a problem with the fuel temperature sensor B circuit. In this article, we’ll dive into what this code means, what causes it, how to diagnose it, and how to fix it.

What is the P0189 Code?

The P0189 code indicates that there is a high input signal in the fuel temperature sensor B circuit.

The fuel temperature sensor is located in the fuel tank and measures the temperature of the fuel. This information is used by the engine control module (ECM) to adjust the fuel injection timing and amount to optimize engine performance.

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When the ECM detects that the signal from the fuel temperature sensor B circuit is too high, it triggers the P0189 code and illuminates the check engine light.

This can indicate that there is a problem with the fuel temperature sensor, the wiring, or the ECM itself.

What are the Causes of the P0189 Code?

There are several possible causes of the P0189 code, including:

  1. Faulty fuel temperature sensor: Over time, the fuel temperature sensor can wear out or become damaged, which can cause it to send a high input signal to the ECM.
  2. Wiring issues: Faulty wiring connections or damaged wires can cause the signal from the fuel temperature sensor to be disrupted or distorted, leading to a high input signal.
  3. ECM malfunction: A malfunctioning ECM can misinterpret the signal from the fuel temperature sensor and trigger the P0189 code.
  4. Fuel contamination: If there is water or other contaminants in the fuel, it can cause the fuel temperature to be higher than normal, which can trigger the P0189 code.

How to Diagnose the P0189 Code?

To diagnose the P0189 code, a mechanic will typically perform the following steps:

  1. Use a diagnostic scanner to read the code and any additional codes that may be present.
  2. Inspect the wiring and connections of the fuel temperature sensor to ensure that they are all intact and in good condition.
  3. Test the fuel temperature sensor using a multimeter to check for proper resistance and voltage readings.
  4. Check the fuel for contamination or impurities that could affect the temperature readings.
  5. Test the ECM for faults using a diagnostic scanner or computerized diagnostic tool.

How to Fix the P0189 Code?

Once the cause of the P0189 code has been identified, the mechanic can recommend the appropriate fix, which may include:

  1. Replacing the fuel temperature sensor: If the sensor is faulty, replacing it will solve the problem.
  2. Repairing or replacing damaged wiring: If the wiring is damaged or has faulty connections, repairing or replacing it will solve the problem.
  3. Replacing the ECM: If the ECM is malfunctioning, it will need to be replaced.
  4. Draining and refilling the fuel tank: If the fuel is contaminated, draining and refilling the tank with clean fuel can solve the problem.


The P0189 code can be a frustrating problem for car owners, but it’s important to address it quickly to avoid any damage to the engine. By understanding what causes the code and how to diagnose and fix the issue, you can get your car back on the road in no time.


Q: Can I still drive my car with the P0189 code?
A: It’s generally not recommended to drive with the check engine light on, as it can indicate a problem that could affect the performance of the engine.

Q: Is the P0189 code serious?
A: While it’s not as serious as some other codes, such as those related to the engine or transmission, it’s still important to address the issue to avoid any damage to the engine.

Q: How much does it cost to fix the P0189 code?
A: The cost of fixing the P0189 code can vary depending on the cause of the issue, but it typically ranges from $100 to $500.

Q: What happens if I don’t fix the P0189 code?
A: If left unaddressed, the P0189 code can lead to poor engine performance and reduced fuel efficiency.

Q: How can I prevent the P0189 code from happening?
A: Regular maintenance, such as fuel filter changes and fuel system cleanings, can help prevent the P0189 code from occurring.