For 1990-2009 cars

Table 1: | Fuel Level Sensor Inspection

Fuel Supply System
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### 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 ignition is ON or the engine is running.

### Conditions for Setting the DTC

• | A voltage range check -- The fuel level sensor input circuit voltage is more than a specified value.

• | The condition present continuously for at least 5 seconds.

### 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.

• | The PCM will enter the Fail-Safe Function and operate as if the fuel level is 100 percent (full).

### 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

The scan tool will display a default value of 100 percent all the time when a CURRENT fuel level sensor circuit DTC is present. Clear any current or stored fuel level sensor circuit DTCs before diagnosing the fuel level sensor circuit with a scan tool.

An open or a short to ignition voltage in the fuel level sensor circuit will indicate a 0 percent fuel level on the scan tool (empty fuel tank).

A short to ground in the fuel level sensor circuit will indicate a 100 percent fuel level on the scan tool (full fuel tank).

Check the resistance of the fuel level sensor at the following positions:

#### Fuel Level Sensor Inspection

Fuel Level Position | Resistance Measurement
--- | ---
Full Tank | 10 ohms or less
Half Tank | 30 to 35 ohms
Empty Tank | 100 ohms or more

Check for a faulty electrical connection at the PCM.

If the DTC P0463 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 P0463 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0463 appears in the Not Ran Since Code Cleared list, the P0463 diagnostic has not yet run. When the DTC P0463 does not appear in the Not Ran Since Code Cleared list, the P0463 diagnostic has run. If the MIL is NOT ILLUMINATED, and there is no PENDING DTC Status in DTC Information, the P0463 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.

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 P0463 cannot be duplicated, 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.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and 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.

2. This step determines if the fault that set the DTC is still present.

3. This step checks for a faulty PCM. If the fuel gauge indicates the correct amount of fuel, there is a voltage fault within the PCM.

4. In order to locate the C401 connector follow the fuel tank wire harness to the square pass through grommet. The grommet is 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.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn ON the ignition, leaving the engine OFF.
2. Clear the DTC information with a scan tool.
3. Start the engine.
4. Operate the engine for 1 minute.

Is there a PENDING or CURRENT DTC P0463 set?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn ON the ignition, leaving the engine OFF.
2. Observe the fuel gauge on the I/P.
3. ADD 3 gallons of fuel to the fuel tank if the fuel gauge is indicating EMPTY.

Does the fuel gauge indicate EMPTY?

--

Go to Step 4

Go to Step 11

4 |

1. Disconnect the fuel level sensor harness connector C401 which is located at the rear of the vehicle below the left tail light assembly.
2. Turn ON the ignition, leaving the engine OFF.
3. Measure the signal voltage from the fuel level sensor wire, PCM side, using a DMM.

Is the voltage within the specified value?

7-8 volts

Go to Step 5

Go to Step 7

5 |

1. Turn OFF the ignition.
2. Reconnect the C401 electrical connector.
3. Remove the fuel tank from the vehicle. Refer to Fuel Tank Replacement .
4. Disconnect the fuel level sensor electrical connector at the fuel level sensor.
5. Turn ON the ignition, leaving the engine OFF.
6. Measure the signal voltage from the fuel level sensor wire, PCM side, using the DMM.

Is the voltage within the specified value?

7-8 volts

Go to Step 6

Go to Step 8

6 |

1. Check for a proper ground connection at the fuel tank.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 9

7 |

1. Check for a short to ignition positive voltage in the fuel level sensor signal circuit.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 10

8 | Repair the open 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 12 | --
9 | Replace the fuel level sensor. Refer to Fuel Sender Assembly Replacement . Is the action complete? | -- | Go to Step 12 | --
10 | Repair the open in the fuel level sensor signal wire between the harness connector C401 and the S258. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 12 | --
11 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 12 | --
12 |

1. Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to Diagnostic Trouble Code (DTC) List

System OK