P0461

Schematic:

Fuel level information is accomplished by using two variable resistance fuel level sensors in series, which vary resistance according to changes in the level of fuel in the fuel tank. The ECM supplies a 5 volt reference through a pull-up resistor to the primary fuel level sensor, which is part of an assembly to the primary fuel pump module (right side of fuel tank). The primary fuel level sensor is electrically connected to the secondary fuel level sensor, which is part of an assembly to the secondary fuel pump module (left side of fuel tank). The secondary fuel level sensor is connected to ground. When the level of fuel in the fuel tank is high, each sensor resistance is low (low voltage on signal line). As the fuel level decreases, the sensor resistances increase (higher voltage on signal line). The ECM monitors the fuel level sensor signal voltage to determine fuel tank level. The fuel level sensor signal voltage ranges between 400 mV to 2.5 volts with each sender arm at the highest and lowest positions. The ECM will send this fuel level information over the CAN link to the BCM. The BCM in turn will average this information with respect to vehicle speed, then send it over the Class II link to the I/P cluster who will position the fuel gauge. DTC P0461 will set if the ECM calculated fuel consumption deviates by a certain amount based on the fuel level sensor reading.

DTC PARAMETERS
DTC P0461 will set if the fuel level deviates more than 12 L (3.17 gallons) the ECM has calculated that 14 L (3.70 gallons) after should have been consumed.

DTC P0461 diagnostic runs once per ignition cycle.

P0461 is a type D DTC

DIAGNOSTIC AIDS

IMPORTANT: A mechanical venturi jet pump is located in the fuel tank as an assembly to the secondary fuel pump module (left side of fuel tank). This module is on the opposite side of the fuel tank to that of the fuel pump. The jet pump function is to move fuel from one side of the tank over the hump to the other side. If fuel is added to the fuel tank, the primary fuel level sensor will increase resistance, while the secondary fuel level sensor remains the same until enough fuel is added to make it over the hump. AS A RESULT, IT MAY BE NORMAL TO HAVE EACH SENSOR READ DIFFERENT RESISTANCE VALUES WHEN THE VEHICLE IS ON LEVEL GROUND.

NOTE:
^ It is the sum of the resistances that make the fuel level accurate.
^ FUEL LEVEL SENSOR voltage on Scan tool is instantaneous, NOT averaged.

Use Scan tool to monitor FUEL LEVEL SENSOR voltage while raising vehicle from the rear. Voltage should change indicating moving floats. NOTE: Voltage may not change if fuel level is too high or too low.

Possible causes of static fuel level:
^ Primary or secondary fuel level sensor sweep arm stuck or the sweep arm is bent

NOTE: A perforated primary or secondary fuel level sensor float is NOT possible.

Each fuel level sensor resistance: 19 ohms with float at top position (full fuel tank); though 125 ohms with float at bottom position (empty fuel tank).

The fuel tank inline harness connector contains a voltage tap wire that is connected between the primary and secondary fuel level sensor. As a result, this wire in conjunction with the 5 volt supply and reference return wire to the sensors may be used to take a resistance measurement of each sensor.