Technical Description of OBD-II Trouble Code
High Input in Fuel Level Sensor “B” Circuit
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The fuel level sensor (sender) is typically located in the fuel tank and is usually integrated with the fuel pump module. In most cases, the fuel pump module needs to be replaced in order to replace the fuel level sensor, although there are exceptions. The sensor consists of a float attached to an arm that moves along a resistor. The resistor is either grounded to the tank or frame, or it has a dedicated ground circuit. The sender is supplied with voltage, and the ground path changes according to the fuel level. The amount of voltage supplied depends on the system, but 5 volts is common.
As the fuel level changes, the float moves the arm, which in turn changes the resistance to ground. This variation in resistance affects the voltage signal. The signal may be sent to a fuel pump computer module or directly to the instrument cluster module, depending on the system. In some cases, the fuel pump computer module only monitors the resistance to ground and then relays the fuel level information to the instrument panel. If the fuel level signal to the fuel pump module (or instrument cluster module or PCM) exceeds 5 volts for a specific duration, the module monitoring the fuel level circuit will store this fault code.
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:
Symptoms
The symptoms of a P2068 DTC may include:
Causes
Possible causes of a P2068 code include:
Possible Solutions
Fuel pump senders typically last the lifespan of the fuel pump. If you have this code, visually inspect the fuel tank and wiring harness for any damage. Look for signs of impact that may have damaged the fuel pump or sender. Check for a missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Examine the wiring harness connector for any damage. Repair as necessary. Determine the type of system you have and verify the presence of voltage at the fuel level sensor in the fuel pump wiring harness. If voltage is not present, repair any open or short in the wiring.
You can perform a voltage drop test on the ground circuit to identify any high resistance path in the ground circuit. Use a voltmeter to connect one lead to the battery ground post and the other lead to the fuel level sensor ground at the tank. Turn the key on (preferably with the engine running). Ideally, the voltage drop should be 100 millivolts or less (0.1 volts). A voltage close to 1 volt indicates a current or developing problem. Repair or clean the fuel level sensor ground as needed. It is possible that the instrument cluster has failed internally or on the printed circuit board (if applicable). Testing these components can be challenging for non-professionals. However, if you have access to a wiring diagram, you may be able to remove the cluster and visually inspect the circuit for damage on the printed circuit board. Otherwise, you will need a scan tool that can communicate with the instrument cluster.
A simple way to test the fuel level circuit is to provide a good ground to the fuel level sensor at the fuel tank connector. With the key on, the fuel gauge should move to one extreme or the other. Removing the ground path completely should cause the gauge to move in the opposite direction. If the gauge responds accordingly, it indicates that the wiring supplying voltage and ground to the fuel level sensor is functioning properly and that the instrument cluster is likely in good condition. The most likely culprit would be the fuel level sensor itself. Accessing the fuel pump module in the tank may require removing the fuel tank. While it is not impossible for the PCM or BCM (Body Control Module) to fail, it is highly unlikely. Therefore, it is not advisable to suspect these components as the first cause.
