What does it mean?
As we know, the modern fuel injection and ignition system is a complex coordination of sensor readings and actuator outputs, all with the aim of delivering the most efficient power. The engine control module (ECM) uses various sensors to determine how much fuel to inject at any given moment, making precise calculations based on air flow and temperature, engine load and speed, driver demand, and a number of others.
Because the density of the fuel depends on its temperature, the ECM needs to take this into account when calculating fuel injector pulse. Without knowing fuel temperature, the ECM would command the same fuel delivery at all temperatures, resulting in richer or leaner combustion than ideal. On engines equipped with a fuel temperature sensor (FTS), this results in finer control of air-fuel ratio and lower emissions.
Earlier vehicles not equipped with an FTS achieved similar results using feedback from the AFR sensors. The ECM continually monitors the resistance of the FTS, calculating temperature based on those readings. If there is a fault in the FTS or FTS circuit, the ECM will illuminate the malfunction indicator lamp (MIL) and set a diagnostic trouble code (DTC) in memory.
Specifically, if the ECM detects a temperature change in excess of ±10 °C (±18 °F) / 100 ms, it interprets this as an intermittent circuit fault, setting DTC P0184 – “Fuel Temperature Sensor “A” Circuit Intermittent.” Note: Regardless of the code and the system affected, the word “Intermittent” refers to the fact that there is a sporadic, unpredictable, or, well, intermittent fault in that system.
The most likely causes of codes that relate to intermittent faults include poor connections in both live and ground circuits, as well defective switches, relays, and sensors. Intermittent faults can be extremely difficult to trace and fix, since code readers generally do not specify in which part of the circuit the problem lays.
For instance, the fault could be an intermittent interruption of the reference voltage (power supply), or, as often happens, the problem could be an intermittent break in the signal voltage to the PCM (Powertrain Control Module) due to a failing sensor, wiring issues, or defective electrical connector(s).
Note that the word “intermittent” often means different things to different applications; some systems will set a code the first time an intermittent fault occurs, while others will only do so after several failure cycles. In some cases, it may be necessary to allow the fault to worsen before an accurate and definitive repair can be made.