Circuit Description
The fuel level sensor measures fuel level changes within the fuel tank and changes resistance based on fuel level. The powertrain control module (PCM) monitors changes in the resistance of the sensor to determine fuel level. When the fuel tank is full, the sensor resistance is high, and the PCM senses high signal voltage. When the fuel tank is empty, the sensor resistance is low, and the PCM senses a low signal voltage. The PCM uses inputs from the fuel level sensor to calculate the total fuel remaining in the fuel tank. This information is then sent to the Instrument via the Class 2 serial data circuit and the powertrain interface module (PIM). When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
Fuel level sensor voltage is below 0.5 volts.
Action Taken When the DTC Sets
| • | The multifunction display (MFD) displays the LOW FUEL message. |
| • | The fuel gage defaults to empty. |
| • | The PCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The Check Powertrain malfunction illumination light (MIL) will not be activated. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. |
| • | The (MFD) in the Instrument cluster, will display a message at key-on and key-off. |
Conditions for Clearing the DTC
| • | A Last Test Failed (current DTC), 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. |
| • | The PCM receives the clear code command from the scan tool. |
Diagnostic Aids
Important: When inspecting for a deformed or a 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 resistance values are not the same, refer to Fuel Tank Replacement in Engine Controls.
| • | Use the Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data may aid in determining the number of miles since the DTC set. |
| • | The Fail Counter and Pass Counter can also aid in determining the number of ignition cycles that the diagnostic reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions (RPM, engine load, vehicle speed, temperature, etc.). This will isolate when the DTC failed. |
| Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics | ||||
1 | Did you perform the IPC Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that the Fuel Level parameter is less than the specified value? | 4% | Go to Step 3 | Go to Diagnostic Aids |
Does the scan tool indicate that the Fuel Tank Level Remaining parameter is greater than the specified value? | 98% | Go to Step 5 | Go to Step 4 | |
4 | Test the signal circuit of the fuel level sender for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
5 | Test the signal circuit of the fuel level sensor for a short to ground between C402 and the fuel level sensor. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 |
6 | Inspect for poor connections at the harness connector of the fuel level sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
7 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
8 | Replace the fuel level sensor. Refer to Fuel Sender Assembly Replacement in Engine Controls. Did you complete the replacement? | -- | Go to Step 10 | -- |
9 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls. Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
