| Table 1: | Fuel Level Sensor Inspection |
Circuit Description
The powertrain control module (PCM) uses the fuel level input from the fuel level sensor in order to calculate the expected vapor pressures within the fuel system. Vapor pressures vary as the fuel level changes. Vapor pressure is critical to determining if the EVAP control system is operating properly. Fuel level information is used in determining whether to run an EVAP control system diagnostic. A fuel level that is too high or too low may prevent the EVAP control system diagnostics from accurately detecting a fault.
Condition for Running the DTC
| • | The engine is running. |
| • | Engine speed is more than 1,000 RPM. |
| • | Vehicle speed is indicated. |
| • | The PCM is calculating fuel volume usage based on fuel injector activity. |
Conditions for Setting the DTC
The change in the fuel level reading is less than expected when compared to the calculated fuel volume usage.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutively passing trips without a fault present. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the scan tool Clear DTC Information function or disconnect the PCM battery feed in order to clear the DTC. |
Diagnostic Aids
Check for any of the following conditions:
| • | If a DTC P0463 is also displayed, diagnose that DTC first. |
| • | A stuck fuel level sensor may cause a DTC P0461 to set. |
| • | A faulty electrical connection at the PCM |
The scan tool will display a default value of 100 percent all the time when a fuel level sensor circuit DTC is present. Any current or stored fuel level sensor circuit DTCs (DTC P0463 or P0461) must be cleared before diagnosing the fuel level sensor circuit with a scan tool.
An open in the fuel level sensor circuit will indicate a 0 percent fuel level (empty fuel tank), while a short to ground in the fuel level sensor circuit will indicate a 100 percent fuel level (full fuel tank).
Check the resistance of the fuel level sensor at the following positions:
Fuel Level Position | Resistance Measurement |
|---|---|
Full Tank | 10 ohms or less |
Half Tank | 30 to 35 ohms |
Empty Tank | 120 ohms or more |
An intermittent malfunction may be caused by a problem in the fuel level sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals |
| • | Improper mating of terminals |
| • | Broken electrical connector locks |
| • | Improperly formed or damaged terminals |
| • | Faulty terminal to wire connections |
| • | Physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Corrosion of electrical connections, splices, or terminals |
If the DTC P0461 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0461 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0461 appears in the Not Ran Since Code Cleared list, the P0461 diagnostic has not yet run. When the DTC P0461 does not appear in the Not Ran Since Code Cleared list, the P0461 diagnostic has run. If the MIL is NOT ILLUMINATED and there is no PENDING DTC Status in DTC Information, the P0461 diagnostic has passed. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT or PENDING status, in order to determine the outcome of the diagnostic test involved.
If you cannot duplicate the DTC P0461, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and to store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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In order to locate the C401 connector follow the fuel tank wire harness to the square pass through grommet, located in the frame rail below the left side taillight assembly. Gently pull the grommet and harness out of the frame rail. The C401 connector is located a couple of inches from the pass through grommet.
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This step checks the circuit from the fuel level sensor to the PCM. Because the scan tool will display a default value of 100 percent all the time when a fuel level sensor circuit DTC is present, any current or stored fuel level sensor circuit DTCs (DTC P0463 or P0461) must be cleared before reading the fuel level parameter on the scan tool.
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This step checks for a faulty fuel level sensor.
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This step checks for an open in the fuel level sensor signal circuit from the I/P fuel gauge to S258 only. If there was an open in the fuel level sensor signal circuit between S258 and the fuel level sensor, the PCM would see a high voltage signal and set a DTC P0463 instead of a P0461.
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This step checks whether the malfunction that caused the DTC P0461 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool Clear DTC Information function, the DTC P0461 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0461 appears in the Not Ran Since Code Cleared list, the P0461 diagnostic has not yet run. When the DTC P0461 does not appear in the Not Ran Since Code Cleared list, the P0461 diagnostic has run. If the MIL is NOT ILLUMINATED and there is no PENDING DTC Status in DTC Information, the P0461 diagnostic has passed. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT or PENDING status, in order to determine the outcome of the diagnostic test involved.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | ||||||
Is the voltage near the specified value? | 7-8 volts | Go to Step 3 | Go to Step 8 | |||||
3 |
Is the voltage near the specified value? | 7-8 volts | Go to Step 4 | Go to Step 12 | ||||
4 |
Is the voltage near the specified value? | 7-8 volts | Go to Step 5 | Go to Step 9 | ||||
5 |
Was a repair necessary? | -- | Go to Step 14 | Go to Step 6 | ||||
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Important: In order to avoid an incorrect fuel level reading on the scan tool, any current or stored fuel level DTCs should be cleared.
Does the fuel tank level value on the scan tool increase and then decrease steadily when the float is swept from one end to the other? | -- | Go to Diagnostic Aids | Go to Step 7 | |||||
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Important: The fuel gauge responds slowly to changes in the position of the fuel sensor float. Continue to move the fuel tank sensor float from the empty position, and then back to the full position, while observing the fuel gauge on the I/P. Does the I/P fuel gauge indicate a full and then an empty fuel tank when the float is swept from one end to the other? | -- | Go to Step 13 | Go to Step 10 | |||||
8 |
Was a repair necessary? | -- | Go to Step 14 | Go to Step 11 | ||||
9 | Repair the open or the short in the fuel level sensor signal wire between the fuel level sensor harness connector C401 and the fuel level sensor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 14 | -- | ||||
10 | Replace the fuel level sensor. Refer to Fuel Sender Assembly Replacement . Is the action complete? | -- | Go to Step 14 | -- | ||||
Was a repair necessary? | -- | Go to Step 14 | ||||||
12 | Repair the open in the fuel level sensor signal circuit between the PCM and the I/P fuel gauge. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 14 | -- | ||||
13 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 14 | -- | ||||
Are any DTCs displayed on the scan tool? | -- | System OK |
