For 1990-2009 cars

Table 1: | Fuel Level Sensor Inspection

Schematic reference: Engine Controls Schematics

### 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.

### Conditions for Running the DTC

Engine is running.

### Conditions for Setting the DTC

• | A voltage range check indicates that the voltage is greater than the specified value.

• | The condition is present for 0.5 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.

### Conditions for Clearing the MIL/DTC

• | The MIL will turn OFF after three consecutively passing trips without a fault present.

• | A History DTC will clear after 40 consecutive warm-up cycles without a fault.

• | DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

### Diagnostic Aids

An open in the fuel level sensor circuit will indicate a 0% fuel level (empty fuel tank), while a short to ground in the fuel level sensor circuit will indicate a 100% fuel level (full fuel tank).

Check for a corroded or loose fuel level sensor chassis ground. Operate the tail lamps and brake lamps while checking the fuel level sensor reading on a scan tool. Increasing the current flow through the G400 chassis ground can reveal a faulty circuit connection.

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 | 120 ohms or more

Check for a faulty electrical connection at the PCM.

An intermittent malfunction may be caused by a fault 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 a fault is present.

3. This step checks the circuit from the fuel level sensor to the PCM. Because the scan tool will display a default value of 100% all the time when a fuel level sensor circuit DTC is present, any current or stored fuel level sensor circuit DTCs (DTC P0461 or P0463) must be cleared before reading the fuel level parameter on the scan tool.

4. This step checks for a faulty fuel level sensor.

Step | Action | Values | 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. Perform the scan tool clear DTC information function.
3. Operate vehicle within the Freeze Frame conditions as noted.

Is a DTC P0463 set?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Remove the rear seat cushion. Refer to Seat Cushion Replacement - Rear in Seats.
2. Disconnect the fuel level sensor harness electrical connector C310.
3. Turn ON the ignition, leaving the engine OFF.
4. Measure the signal voltage from the fuel level sensor connector YEL/RED wire, (PCM side), using a DMM.

Is the voltage near the specified value?

7-8 volts

Go to Step 4

Go to Step 8

4 |

1. Reconnect the fuel level sensor harness connector C310.
2. Remove the fuel tank from vehicle. Refer to Fuel Tank Replacement .
3. Disconnect the fuel sender assembly electrical connector at the fuel sender.
4. Measure the signal voltage from the fuel level sensor connector YEL/RED wire (PCM side), with a DMM connected to ground.

Is the voltage near the specified value?

7-8 volts

Go to Step 5

Go to Step 9

5 |

1. Check for a proper ground connection at the fuel tank.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 6

6 | Important: In order to avoid an incorrect fuel level reading on the scan tool, any current or stored fuel level DTCs should be cleared.

1. Remove the fuel sender assembly from the fuel tank. Refer to Fuel Sender Assembly Replacement in Engine Controls.
2. Reconnect the fuel tank level sensor electrical connector.
3. Monitor the fuel tank level sensor parameter on the scan tool while slowly moving the fuel level sensor float from the empty position and then back to the full position. Repeat the procedure several times.

Does the fuel tank level display on the scan tool increase to the first specified value and then decrease steadily to the second specified value when the float is swept from one end to the other?

90%

0%

Fault not Present-Go to Diagnostic Aids

Go to Step 7

7 | Important: The fuel gauge responds slowly to changes in the position of the fuel sensor float. Continue to slowly move the fuel level 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 an empty fuel tank when the float is swept from one end to the other?

--

Go to Step 13

Go to Step 10

8 |

1. Check for an open or a short in the fuel level sensor signal wire between the harness connector C310 and the PCM.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 11

9 | Repair the open or the short in the fuel level sensor signal (input) wire between the fuel level sensor harness connector C310 (located under the rear seat cushion) and the fuel sender assembly. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 15 | --
10 | Replace the fuel level sensor. Refer to Fuel Level Sensor Replacement . Is the action complete? | -- | Go to Step 15 | --
11 |

1. Turn OFF the ignition.
2. Disconnect fuel level sensor harness.
3. Disconnect the PCM electrical connector.
4. Turn ON the ignition, leaving the engine OFF.
5. Measure the voltage from fuel level sensor signal (input) terminal (harness side), using a DMM.

Does the DMM read within the specified value?

7 to 8 volts

Go to Step 14

Go to Step 12

12 |

1. Check for an open or a short in the fuel level sensor signal circuit between the PCM and the I/P fuel gauge.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Instrument Cluster System Check in Instrument Panel, Gauges, and Console

13 |

1. Check for an open in the fuel level sensor signal circuit between the PCM and the I/P fuel gauge.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 14

14 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 15 | --
15 |

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 the Applicable DTC Table

System OK