P0180 Fuel Temperature Sensor A Circuit Malfunction
OBD-II Trouble Code Technical Description
Fuel Temperature Sensor A Circuit Malfunction
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles (Nissan, Ford, Fiat, Chevrolet, Mercedes, Dodge, etc.). Although generic, the specific repair steps may vary depending on make/model.
If your OBD II equipped vehicle has stored a code P0180; it simply means that the powertrain control module (PCM) has detected a voltage signal from the fuel temperature sensor/flex fuel sensor or circuit "A" that is not within a programmed range. "A" refers to an area of circuitry as opposed to a particular circuit or component.
The fuel temperature sensor is typically integrated into a single housing (along with the flex fuel sensor) known as a fuel composition sensor. It is actually a small computerized device designed to provide the PCM with an accurate fuel composition and fuel temperature reading.
Fuel which passes through the inline sensor is monitored to determine what degree of ethanol, water, and other contaminants is present. The fuel composition sensor calculates fuel composition and fuel temperature and inputs an electrical signal to the PCM that reflects not only what contaminants are present but also to what degree the fuel has been contaminated. The contamination is measured according to the percentage of contaminants to fuel and is received by the PCM as a square waveform of voltage. The waveform pattern varies in frequency depending upon the degree of contaminants present in the fuel; the closer the waveform frequency, the higher the degree of fuel contamination. This composes the vertical portion of the waveform. The fuel composition sensor monitors the amount of ethanol present in the fuel separately from other contaminants. Flex fuel vehicles are designed to function efficiently when fuel composition levels are as high as eighty-five-percent ethanol.
The horizontal portion of the waveform, or the pulse width, indicates fuel temperature. The greater the pulse width speed, the higher the temperature of the fuel passing through the fuel composition sensor. Pulse width modulation varies (on most applications) between one and five-milliseconds (hundredths-of-a-second).
If the PCM detects an input signal from the fuel composition sensor that indicates that the fuel temperature is not within a programmed range, or if the fuel temperature varies from ambient temperature (intake air temperature on some models) by a greater degree than expected, a P0180 code will be stored and a malfunction indicator lamp (MIL) may be illuminated. Some models may require multiple ignition cycles (with a failure) for MIL illumination.
Photo of different fuel temperature sensors:
Code Severity & Symptoms
Fuel temperature is monitored by the PCM to calculate fuel delivery strategy in flex fuel vehicles so a code P0180 should be treated as severe.
Symptoms of this code may include:
Causes
Potential causes for this code to set are:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.
To diagnose a code P0180, I would typically gain access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), an oscilloscope, an infrared thermometer, and a vehicle information source like All Data DIY. Some scanners have a DVOM and a portable oscilloscope built-in; that would serve you well in this scenario.
I like to begin any diagnosis with a visual inspection of all related wiring harnesses and connectors. Repair or replace damaged or burnt components as required and retest the system. When multiple failure cycles are required for MIL illumination, I have found that using OBD II readiness mode helpful. When I have completed my repairs, I clear the codes and operate the vehicle normally. If the PCM enters readiness mode, I know that my repairs were successful. If the code is reset, I know that a malfunction still exists.
The fuel temperature sensor (integrated into the fuel composition sensor) is typically supplied with a five-volt reference voltage and a ground. The variable resistance sensor completes the circuit. Use the DVOM to test reference voltage and ground at the fuel temp sensor connector. If reference voltage is not present, use the DVOM to test the corresponding circuits at the PCM connector. Repair open circuits as required if there is a reference voltage signal at the PCM connector. Caution: See note at the bottom of the page regarding disconnecting the controllers. If no reference voltage is present at the PCM connector, suspect a faulty PCM or a programming error. PCM replacement or reprogramming will require professional assistance. If there is no fuel temp sensor ground, use your vehicle information source and locate the appropriate ground to make sure that it is secure.
If the reference and ground are present at the fuel temperature sensor A connector, connect the test leads of the oscilloscope to the appropriate circuits and observe live data in the form of waveform patterns. Use the infrared thermometer to measure actual fuel temperature and compare it with the temperature reflected by the waveform patterns on the oscilloscope. If the fuel temperature reflected by the fuel temperature sensor fails to coincide with that of the thermometer, suspect that the fuel temperature sensor is defective.
Additional diagnostic notes:
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"Delete Error Code Permanently, Disable DTC Error Code Function for p0180 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p0180 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0180.
