P1172

CIRCUIT DESCRIPTION
The right fuel level sensor measures fuel level changes within the right fuel tank. When the fuel level is high the sensor signal voltage is high. When the fuel level is low the sensor signal voltage is low. The control module uses inputs from the left fuel level sensor and the right fuel level sensor in order to calculate the total fuel remaining in both sides of the fuel tank. The control module sends this information via class 2 to the instrument panel cluster.

This diagnostic tests for a restriction in the fuel system between the secondary and primary of the fuel tank. If the control module determines that the fuel level, secondary side of tank, signal appears to be stuck based on a lack of signal variation expected during normal operation, this DTC sets.

The fuel pump also supplies a small amount of pressurized fuel to the siphon jet pump through the fuel feed pipe. The pressurized fuel creates a venturi action inside the siphon jet pump. The venturi action causes the fuel to be drawn out of the secondary side of the fuel tank. Fuel is then transferred from the secondary side of fuel tank to the primary side of fuel tank through the internal fuel transfer tube.

The fuel level in the fuel tank will equalize when the following occur:
- The electric fuel pump is operating.
- The fuel level is more than 50 percent.
- The vehicle is being re-fueled.

CONDITIONS FOR RUNNING THE DTC
The engine is running.

CONDITIONS FOR SETTING THE DTC
- The engine control module (ECM) does not detect a difference of at least 3.7 liters (1 gallon) between the fuel level 1 and fuel level 2 sending units.
- Engine operating more than 2 minutes.

ACTION TAKEN WHEN THE DTC SETS
- The control module stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will not illuminate.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
- The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
- A current DTC Last Test Failed clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.

DIAGNOSTIC AIDS

IMPORTANT: High resistance in the secondary fuel level sensor circuit may set this DTC. When inspecting for a deformed or warped fuel tank, measure the resistance of the suspect fuel level sensor at empty, with the sensor in the fuel tank, and again with the sensor removed from the fuel tank. The measured resistance values should be the same at empty. If the measured values are not the same, refer to Fuel Tank Replacement.

Depending on the current fuel level, it may be difficult to locate a malfunctioning sending unit. The malfunction may only occur when the fuel level is full or near empty. The fuel sending unit may need to be removed for further diagnosis. A fuel level sensor that has an intermittent condition causes this DTC to set. Remove the fuel level sensor.The resistance of the sensor should change between 40-250 ohms. Replace the sensor if the resistance did not change or was out of range.

TEST DESCRIPTION

Steps 1-2:

Steps 3-4:

Steps 5-8:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if a condition current.
4. This step verifies possible component problems within the fuel tank.