P0184 OBD-II Trouble Code: An Intermittent Error on the Fuel Temperature Sensor “A” Circuit

The Definition of Trouble Code P0184

An intermittent error on the fuel temperature sensor “A” circuit.
In general, trouble code P0148 means that there is an erratic or unstable voltage signal that is being detected by the PCM on the fuel temperature sensor along with the circuit. The signal code might also be more specific to the “A” part of the circuit, which is an area of the sensor circuitry.

If you use a vehicle with the OBD-II feature equipped on it, then the fuel temperature sensors are usually integrated into the housing of the fuel composition sensor. This component is important because it will supply the PCM with an accurate reading and analysis for the fuel composition and temperature. The fuel composition sensor itself is normally located between the fuel rail and the fuel tank. You can notice it by looking for a small component with a computerized mechanism.

The fuel composition sensor works by evaluating the amount of compounds that form the fuel composition in the tank. Normally, your fuel should have a normal amount of water, ethanol, and other contaminants in it. The sensor will detect the level of contamination by determining the square waveform patterns, which represent the voltage, and will send the reading to the PCM. If the sensor reads shorter waveforms frequencies, then the PCM will read that there is a high concentration of contaminants in the fuel. Aside from analyzing the waveform frequency, the sensor will also analyze the vertical posting from the waveform patterns.

Vehicles with flex-fuel design will usually be able to function normally with high levels of contaminants in the fuel, with the amount reaching around 85% ethanol. The PCM will analyze the composition by reading the horizontal portion of the waveform frequency. This will also represent the accurate reading for fuel temperature. A high temperature of the fuel will be represented by a broader width on the waveform. For vehicles with an OBD-II system, the pulse width variation is normally between 1 – 5 milliseconds.

If the analysis from the sensors states that the fuel temperature signal is unstable or intermittent, then the PCM will store the trouble code P0148 in the memory. Meanwhile, you might also be able to notice the illuminated malfunction indicator lamp. But, the trouble code usually only appears when the erratic reading from the sensor has happened more than a few times, especially on vehicles with OBD-II.

What Does Trouble Code P0184 Mean?

The OBD-II trouble code of P0184 will indicate that the fuel temperature sensor A is experiencing an unstable or intermittent reading. This means that the sensor is not steady and cannot function properly. The other possible cause is that the fuel temperature inside the tank is changing erratically outside of the normal temperature limits.

The Possible Causes of Trouble Code P0184

• The engine control module is detecting a malfunction on the fuel temperature sensor and the sensor is not functioning properly.
• There is corrosion on the sensor related to the sensor.

The Symptoms of Trouble Code P0148

• Unless there is a high level of contamination in the fuel tank, the engine will usually run normally even if the sensor is experiencing an intermittent reading.
• But, an extreme level of additives and contamination in the fuel might also cause unstable sensor readings, which will lead to the fuel freezing too early or boiling at a lower temperature.
• The trouble code P0184 will be stored on the ECM memory and the Check Engine Light will be turned on.
  How Your Mechanics Should Check Trouble Code P0184
• They should analyze the freeze frame data to scan and document the trouble code. Afterward, the code can be cleared before checking and verifying if it still returns.
• They should check the wiring and the connections that go to the sensor. A visual check is required to see if there is any damage to the wiring and connections.
• This should disconnect the sensor first and see if it works under the normal specifications. During this test, they should tap the sensor lightly.

Common Mistakes during the Diagnostics of Trouble Code P0148

There are some steps that can be taken to prevent mistakes when diagnosing this trouble code:

• Always perform a visual check on the sensor connections to ensure that the wirings are in a good condition and they have good contact with the fuel temperature sensor.
• Inspect the level of contaminants because a high level of those elements can cause the unstable performance of the sensors.

How Serious is Trouble Code P0184?

• Some driving anomalies might happen from the erratic reading of the sensor due to the unstable temperature of the fuel in the tank.
• The engine might experience some misfiring or stalling if the fuel in the tank is not at the optimal temperature to support the normal condition of the engine. The unstable reading from the sensor might cause the fuel to get too hot or too cold.

Additional Diagnostics Notes

• You can also check the sensor resistance number using a DVOM. Make sure the number falls within the threshold of the manufacturer’s specifications.
• NOTE: All related controllers need to be disconnected before performing the process to check the resistance number using the DVOM.

The Required Repair Steps for Trouble Code P0184

• Inspect the condition of the fuel temperature sensor and do the replacement of the sensor if needed.
• Inspect the connector or wiring to the sensors to see if they are damaged or defective.
• Inspect and replace the connection between the diesel fuel heater and the fuel temperature sensor.

You might need to start the repair by consulting the technical service bulletins first before taking any repair steps. This is because there is a possibility that you are experiencing a known issue and the bulletins might be a good source of solution for you.

Using a diagnostic scanner that has features for DVOM tester and oscilloscope might also be a good idea to check the trouble code P0184. Another alternative is to use a vehicle information source, such as All Data DIY, and an infrared thermometer to do the job.

But the main thing that you have to do is perform a visual check on the sensor unit along with the related connections prior to the repair. If you find any connections that are corroded, damaged, or burnt, you will need to replace them as soon as possible.

Then, you can try clearing the trouble code and retest the sensor to see if the problem still persists. Make sure to utilize multiple cycles of OBD-II inspection to ensure that the MIL light is not illuminated anymore. If you can verify that the trouble code has been cleared, you can then drive your vehicle normally.

You can check the status of your repair by the mode of your PCM. If the PCM can enter the readiness mode perfectly, then you know that the repair is successful. But if the code resets again, then the failure is still on the sensor. You can proceed by measuring the variable resistance variety using a 5V reference signal and ground connection.

With the help of a DVOM, inspect the reference voltage and ground from the sensor and read the number. If there is no reference voltage detected by the DVOM, you can also check the corresponding circuits around the PCM connector. If you still can’t get a reading for the reference voltage, then it means that the PCM is damaged or experiencing programming errors.

Meanwhile, the oscilloscope can be used to check the waveform patterns and see the level of contaminants in the fuel. You can also add another inspection step by checking the fuel temperature using the infrared thermometer.
Additional Comments Related to the Repair of Trouble Code P0184

Trouble code P0184 is usually found on vehicles that are equipped with diesel engines. Those vehicles usually have a fuel heater that is used to monitor the fuel temperature inside the tank. If the problem code appears, make sure that you follow the recommended inspection steps from the manufacturer to avoid any mistake while fixing it.