Technical Description of OBD-II Trouble Code
Circuit Range/Performance Issue with Fuel Level Sensor “B”
What does that signify?
This generic diagnostic trouble code is applicable to all engines equipped with OBDII, but it is more commonly observed in certain Chrysler, GM, Ford, Lincoln, Mercury, Kia, Mazda, Mercedes Benz, Infiniti, Nissan, and Subaru vehicles.
The Fuel Level Sensor (FLS) is typically located in the fuel tank, specifically in the top part where the fuel pump module is situated. The FLS converts the mechanical fuel level into an electrical signal for the Powertrain Control Module (PCM). Usually, the PCM then communicates this information to other controllers through the vehicle’s data communication bus.
The PCM receives this voltage signal to determine the amount of fuel in the tank, monitoring fuel usage and calculating fuel economy. This trouble code is triggered if the input voltage does not match the normal operating voltages stored in the PCM’s memory, even for a brief moment. It also checks the voltage signal from the FLS sensor during the initial Key On phase.
P2066 may be set due to mechanical issues (such as incorrect fuel level rationality, refueling the vehicle with the ignition switch on, or rapid fuel level changes) or electrical issues (FLS sensor circuit). These factors should not be overlooked during the troubleshooting process, especially when dealing with intermittent problems.
The troubleshooting steps may vary depending on the manufacturer, type of FLS sensor, and wire colors. Consult a vehicle-specific repair manual to determine the location of the “B” circuit.
Other related trouble codes for the fuel level sensor B circuit include:
Severity & Symptoms
The severity depends on the nature of the failure. Mechanical failures are more severe, while electrical failures can be compensated for by the PCM. The compensation usually results in the fuel gauge constantly reading Empty or Full.
Symptoms of a P2066 engine code may include:
Potential Causes
The typical causes for this code to be triggered are:
Diagnostic and Repair Procedures
A good starting point is to search for any technical service bulletins (TSBs) related to your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogram available to address this issue, so it is worth checking before going down a potentially incorrect path.
For example, in Ford products where an aftermarket remote start system has been installed, it can cause a false code to be triggered. There is a TSB that covers this issue, and it should be followed to properly diagnose the condition. The TSB also covers auxiliary fuel tanks, recommending against using gravity feed tanks and refueling Ford trucks with the ignition switch in the on position.
Next, locate the Fuel Level Sensor (FLS) in your particular vehicle. This sensor is usually mounted in the fuel tank, possibly in the top part where the fuel pump module is located. Once found, visually inspect the connector and wiring for any signs of scraping, rubbing, bare wires, burn spots, or melted plastic. Disconnect the connector and carefully examine the terminals inside for any signs of burning or corrosion. If cleaning of the terminals is necessary, use electrical contact cleaner and a plastic bristle brush. After cleaning, let it dry and apply electrical grease to the contact points.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if the P2066 code returns. If it does not, then the issue was most likely related to the connections.
This is the most common area of concern for this code, as the fuel tank connections are prone to corrosion issues.
If the P2066 code does reappear, further testing of the FLS sensor and its associated circuits is necessary. With the Key Off, disconnect the electrical connector at the FLS sensor. Connect a Digital Voltmeter (DVOM) black lead to the ground or low reference terminal at the FLS sensor wiring harness connector. Connect the red lead of the Digital Voltmeter to the signal terminal at the FLS sensor wiring harness connector. Turn the Key On but keep the Engine Off. Check the manufacturer’s specifications; the voltmeter should read either 12 volts or 5 volts. If the voltage is incorrect, repair the power or ground wire, or replace the PCM.
If the previous test passes, connect one lead of an ohmmeter to the signal terminal at the sensor and the other lead to the ground or low reference terminal at the sensor. The ohmmeter reading should not be zero ohms or infinite. Refer to the manufacturer’s specifications for the resistance of the sensor to accurately test the resistance at different fuel levels (e.g. 1/2 tank of fuel might read 80 ohms). If the ohmmeter readings do not meet the specifications, replace the FLS.
If all previous tests have passed and the P2066 code continues to appear, it is likely that the FLS sensor has failed. However, a failed PCM cannot be ruled out until the FLS sensor has been replaced. If unsure, seek assistance from a trained automotive diagnostician. PCMs must be programmed or calibrated to the vehicle in order to be installed correctly.
