Circuit Description
The primary fuel level sender and the secondary fuel level sender change resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to determine the fuel level. When the fuel tanks are full, the resistances of both fuel level senders are high, and the ECM senses a high signal voltage on both the signal circuits of the primary fuel level sender and the secondary fuel level sender. When the fuel tanks are empty, the resistances of the fuel level senders are low, and the ECM senses a low signal voltage. The ECM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the percentage of fuel remaining in the tank. The ECM sends the fuel level percentage via the class 2 serial data circuit to the instrument panel cluster (IPC) in order to control the fuel gage.
This diagnostic tests for a stuck secondary fuel level sensor signal. The ECM sets this DTC if the secondary fuel level sensor signal appears to be stuck based on a lack of signal variation expected during normal operation.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1431 Fuel Level Sensor 2 Performance
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The ECM does not detect a change in the secondary fuel level of at least 3 L (0.79 gal) over a distance of 320 km (200 mi).
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 | Yes | No | ||||
|---|---|---|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics | |||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
2 |
Did you find and correct the condition? | Go to Step 4 | Go to Step 3 | ||||
3 | Replace the secondary 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 | ||||
