Circuit Description
The fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the sensor resistance is high and the ECM senses a high signal voltage. When the fuel tank is empty, the sensor resistance is low and the ECM senses a low signal voltage. The ECM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via the class 2 serial data circuit to the instrument cluster in order to control the fuel gage.
This diagnostic tests for a stuck fuel level sensor signal for a single tank or for a stuck primary fuel level sensor signal for dual tanks. The ECM sets this DTC if the fuel level sensor signal appears to be stuck based on a lack of signal variation expected during normal operation.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The ECM does not detect a change in fuel level or a change in the primary fuel level of at least 3.0 L (0.79 gal) over a distance of 320 km (200 miles).
Action Taken When the DTC Sets
| • | The fuel gage defaults to empty. |
| • | The ECM records the operating conditions at the time that the diagnostic test fails. The ECM displays the failure information in the Failure Records on the scan tool. |
Conditions for Clearing the DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The history DTC clears after 40 malfunction free warm-up cycles. |
| • | The ECM receives the clear code command from the scan tool. |
Diagnostic Aids
Use the Freeze Frame/Failure Records data in order to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data may help in determining the number of miles since the DTC set. The Fail Counter and Pass Counter can also help in determining the number of ignition cycles that the diagnostic test reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions, including those for RPM, for engine load, for vehicle speed, for temperature, and for others. This will isolate at what point the DTC failed.
Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics | ||||||||
1 | Did you perform the Instrument Cluster Diagnostic System Check? | -- | Go to Step 2 | |||||
2 |
Did you find and correct the condition? | -- | Go to Step 4 | Go to Step 3 | ||||
3 | Replace the fuel level sensor. Refer to Fuel Sender Assembly Replacement in Engine Controls - 7.8L. Did you complete the replacement? | -- | Go to Step 4 | -- | ||||
4 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||
