GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Generic 🢒 1999 🢒 Unit Repair 🢒 DTC 🢒 DTC P0463 Fuel Level Sensor Circuit High Voltage

Refer to

Cell 22: G103, Fuel Pump


Object Number: 366688 Size: FS
.

Circuit Description

The fuel level sender changes resistance based on fuel level. The fuel level sender has a signal circuit and a ground circuit. The PCM applies a voltage (about 5.0 volts) on the signal circuit to the sender. The PCM monitors changes in this voltage caused by changes in the resistance of the sender to determine fuel level.

When the fuel tank is full, the sender resistance is high, and the PCM's signal voltage is only pulled down a small amount through the sender to ground. Therefore, the PCM will sense a high signal voltage (fuel tank full). When the fuel tank is empty, the sender resistance is low, and the signal voltage is pulled down a greater amount. This causes the PCM to sense a low signal voltage (fuel tank empty).

The PCM uses inputs from the fuel level sender to calculate the total fuel remaining in the fuel tank. This information is then sent to the fuel gauge.

This DTC sets when the PCM senses a signal voltage higher than the normal operating range of the sender.

Conditions for Running the DTC

The ignition switch is in the RUN position.

Conditions for Setting the DTC
    • The fuel level sender voltage is greater the 4.7 volts.
    • All diagnostic conditions met for 10 seconds.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.
    • The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records will store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The PCM will not turn the MIL on.
    • A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
    • The use of a scan tool

Diagnostic Aids

Important: Remove any debris from the PCM module connector surfaces before servicing the PCM module. Inspect the PCM module connector gaskets when diagnosing/replacing the module. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM module.

The vehicle fuel gauge displays empty with this DTC set.

Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

  1. This step determines if the fault is present.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing any DTCs, use the scan tool Capture Info to save Freeze Frame and Failure Records for reference. The control module's data is deleted once the Clear Info function is used.

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

 

2

  1. Turn the ignition off for 15 seconds.
  2. Start the engine.
  3. Operate the vehicle with the conditions required for this diagnostic to run, and as close to the conditions recorded in freeze frame and/or failure records as possible. The special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
  4. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.

Does the scan tool indicate that this diagnostic failed this ignition?

--

Go to Step 4

Go to Step 3

3

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids If any additional DTCs were stored, refer to those table(s).

Were there any additional DTCs stored?

--

Go to the applicable DTC table

Go to Diagnostic Aids

4
  1. Disconnect the Fuel Level sender harness connector.
  2. With a DMM, measure the voltage across the fuel level sender signal circuit to the sensor ground circuit at the harness connector.
  3. Monitor the DMM.

Is the voltage greater than the specified value?

4.70 V

Go to Step 8

Go to Step 5

5
  1. With a DMM measure the voltage across the fuel level sender signal circuit to a known good ground.
  2. Monitor the DMM.

Is the voltage greater than the specified value?

4.70 V

Go to Step 7

Go to Step 6

6
  1. Check the fuel level signal circuit for an open.
  2. If the fuel level signal circuit is open, repair as necessary.

Did you perform a repair?

--

Go to Step 12

Go to Step 10

7
  1. Check the fuel level ground circuit for an open.
  2. If the fuel level ground circuit is open, repair as necessary.

Did you perform a repair?

--

Go to Step 12

Go to Step 10

8
  1. Check for a proper connection at the fuel level sender harness connector.
  2. If a problem is found, repair as necessary. Refer to

Did you perform a repair?

--

Go to Step 12

Go to Step 9

9

Replace the Fuel Level sender.

Is the action complete?

--

Go to Step 12

--

10
  1. Check for a proper connection at the PCM harness connector.
  2. If a problem is found, repair the problem as necessary. .

Did you perform a repair?

--

Go to Step 12

Go to Step 11

11

Important: The new PCM must be programmed.

Replace the PCM.

Is the action complete?

--

Go to Step 12

--

12
  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number which was set.
  6. Operate the vehicle, with the Condition for Setting this DTC, until the scan tool indicates the diagnostic Ran.

--

Go to Step 13

Go to Step 2

13

Does the scan tool display any additional undiagnosed DTCs?

--

Go to the applicable DTC

System OK