Circuit Description
The primary (left) fuel level sensor measures fuel level changes within the left fuel tank and changes resistance based on fuel level. The engine control module (ECM) 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 ECM senses high signal voltage. When the fuel tank is empty, the sensor resistance is low, and the engine control module (ECM) senses a low signal voltage.
The ECM uses inputs from the fuel level sensor to calculate the total fuel remaining in the fuel tanks. This information is then sent to the instrument panel cluster (IPC) via the class 2 serial data circuit.
When the ECM senses a signal voltage higher 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 for the primary (left) level sensor is above 4.5 volts. |
| • | The above conditions are present for greater than 2 minutes. |
Action Taken When the DTC Sets
| • | The DIC displays a LOW FUEL message. |
| • | The fuel gage defaults to empty. |
| • | The ECM records the operating conditions at the time the diagnostic 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 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, load, vehicle speed, temperature, etc.). This will isolate when the DTC failed.
Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Important: 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 resistance values are not the same, refer to Fuel Tank Replacement - Left Side in Engine Controls.
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 Vehicle Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that the Fuel Level Sensor Left Tank parameter is greater than the specified value? | 4.5 V | Go to Step 3 | Go to Diagnostic Aids |
Does the scan tool indicate that the Fuel Level Sensor Left Tank parameter is less than the specified value? | 0.5 V | Go to Step 6 | Go to Step 4 | |
4 | Test the signal circuit of the fuel level sensor for an open, a high resistance, or for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 5 |
5 | Test the low reference circuit of the fuel level sensor for an open, a high resistance, or for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
6 | Test the signal circuit of the fuel level sensor for an open, a high resistance, or for a short to voltage between C420 and the left fuel level sensor. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 |
7 | Test the low reference circuit of the left fuel level sensor for an open, a high resistance, or for a short to voltage between C420 and the left fuel level sensor. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 |
8 | Inspect for poor connections at the harness connector of the left 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 12 | Go to Step 10 |
9 | Inspect for poor connections at the harness connector of the ECM. 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 12 | Go to Step 11 |
10 | Replace the left fuel level sensor. Refer to Fuel Level Sensor Replacement - Left Side in Engine Controls. Did you complete the replacement? | -- | Go to Step 12 | -- |
11 |
Important: Program the replacement ECM. Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
