| Table 1: | Fuel Level Sensor Inspection |
Circuit Description
The powertrain control module (PCM) uses the 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 correctly. 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 Setting the DTC
The change in fuel level from the maximum to the minimum is less than 1 gallon, although the volume of the intake air is calculated at more than 660 kg.
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 that the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 3 consecutive 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
Check for any of the following conditions:
| • | If DTC P0463 is also displayed, diagnose that DTC. |
| • | A stuck fuel level sensor may cause DTC P0461 to set. |
| • | A loose fuel tank baffle that may interfere with the movement of the fuel level sensor float. |
| • | A corroded chassis ground or a loose sensor chassis ground . Operate the tail lamps and the brake lamps while checking the fuel level sensor reading on a scan tool. Increasing the current flow through the G400 chassis ground can expose a faulty circuit connection. |
| • | A faulty electrical connection at the PCM. |
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 open in the fuel level sensor circuit will cause an empty fuel tank indication. A short to ground in the fuel level sensor circuit will cause a full fuel tank indication .
An intermittent malfunction may be caused by a fault in the electrical circuit of the fuel level sensor . Inspect the wiring harness and the components for any of the following conditions:
| • | Backed out terminals |
| • | Incorrect mating of terminals |
| • | Broken electrical connector locks |
| • | Incorrectly formed terminals or damaged terminals |
| • | Faulty terminal-to-wire connections |
| • | Physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Corrosion of electrical connections, of splices, or of terminals |
If the DTC cannot be duplicated, the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC 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 basic checks, and to store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data that was taken when the fault occurred. The information is stored in the scan tool for later reference.
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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 if a fuel level sensor DTC is present. Before reading the fuel level with the scan tool, clear the fuel level sensor DTCs .
-
This step checks for a faulty fuel level sensor.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
2 |
Is the voltage near the specified value? | 7-8 volts | ||
3 |
Is the voltage near the specified value? | 7-8 volts | ||
4 |
Was a repair necessary? | -- | ||
|
Important: Before reading the fuel level with the scan tool, clear any fuel level DTCs.
Does the fuel tank level on the scan tool increase to the first specified value and decrease to the second specified value? | 90% 0% | Go to Diagnostic Aids | ||
|
Important: The fuel gauge responds slowly to changes in the position of the fuel sensor float. Continue to slowly move the float from the empty position to the full position while observing the fuel gauge on the instrument panel. Does the fuel gauge indicate full and empty when the float is moved from one end to the other? | -- | |||
7 |
Was a repair necessary? | -- | ||
8 | Repair the open or the short in the input wire of the sensor between the harness connector C310 and the sensor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
9 | Replace the fuel level sensor. Refer to Fuel Level Sensor Replacement . Is the action complete? | -- | -- | |
10 |
Is the voltage within the specified range? | 7 to 8 volts | ||
11 |
Was a repair necessary? | -- | Go to Instrument Cluster System Check in Instrument Panel, Gauges, and Console | |
12 |
Was a repair necessary? | -- | ||
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
14 |
Are any DTCs displayed on the scan tool? | -- | Go to the applicable DTC table | System OK |
