GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1999 🢒 Intrigue 🢒 Engine 🢒 Engine Controls - 3.5L 🢒 Fuel Level Sensor Diagnosis

Object Number: 293692 Size: LF
Fuel Tank, FTP Sensor, Fuel Pump
Engine Controls Components
OBD II Symbol Description Notice
ESD Notice

Circuit Description

The PCM requires an accurate indication of fuel level for EVAP system diagnosis. The fuel level in the fuel tank changes the rate of vacuum decay for the EVAP system leak DTCs.

The Fuel Level Sensor changes resistance based on fuel level. The Fuel Level Sensor has a signal circuit and a ground circuit. The PCM applies a voltage (about 5 volts) on the signal circuit to the sensor. The PCM monitors changes in this voltage caused by changes in the resistance of the sensor to determine fuel level.

When the fuel tank is full, the sensor resistance is high, and the signal voltage is only pulled down a small amount through the sensor to ground. Therefore, the PCM will sense a high signal voltage (fuel tank full). When the fuel tank is empty, the sensor 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 the input from the Fuel Level Sensor to calculate the fuel level in the fuel tank. Fuel level data is used in the EVAP system diagnostics. Fuel level data is also sent to the IPC via Serial Data.

The normal resistance values of the sensor are as follows:

    • 40ohms plus or minus 2.5ohms = Full
    • 248.5ohms plus or minus 3.3ohms = Empty

This diagnostic table requires the following special tools:

J 33431-C Signal Generator/Instrument Panel Tester

Diagnostic Aids

Important: Fuel level is used to in EVAP system diagnosis. Always diagnose the fuel level sensor before any other EVAP system components or DTCs.

Test Description

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

  1. At 40ohms the scan tool should display Fuel Level close to 0 percent. At 248ohms the display should be close to 100 percent. As the resistance is increased, there should be a corresponding fuel level increase. If any spikes, dips or erratic readings occur, or if the low and high resistance values do not correspond close to 0 percent and 100 percent (values are skewed), the related circuitry should be checked before replacing the sensor.

    2.

  2. Before replacing the sensor, check for the possibility of foreign material in the fuel tank that may inhibit proper float arm movement (including ice). Check for the float arm contacting other components on the fuel pump/sender assembly.

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

2

Is DTC P0462, P0463, or any IPC DTCs set?

--

Go to the applicable DTC table

Go to Step 3

3

  1. Turn the key to Off.
  2. Disconnect the Fuel Level sensor.
  3. Connect Signal Generator/Instrument Panel Tester J 33431-C to the Fuel Level signal and sensor ground circuits, in order to perform the Instrument Sender Substitution Test. Refer to the tool instructions for details on this procedure.
  4. Using the instrument panel tester, set the resistance to the first specified value.
  5. Turn the key to On.
  6. Clear any DTCs using the scan tool.
  7. Observe Fuel Level on the scan tool.
  8. Slowly dial in additional resistance until the second value is reached.

Does the scan tool Fuel Level increase steadily throughout the specified range, from 0 percent to 100 percent?
  1. 40ohms
  2. 248ohms

Go to Step 4

Go to Step 5

4
  1. Turn the key to Off.
  2. Using the instrument panel tester, reset the resistance to the first specified value.
  3. Turn the key to On.
  4. Clear any DTCs using the scan tool.
  5. Observe the fuel gauge in the IPC.
  6. Slowly dial in additional resistance until the second value is reached.

Does the fuel gauge increase steadily throughout the specified range, from Empty to Full?
  1. 40ohms
  2. 248ohms

Go to Step 6

Go to Diagnostic System Check - Instrument Cluster in Instrument Cluster, Panel, and Console

5
  1. Turn the key to Off.
  2. Disconnect the PCM.
  3. Check for the following conditions:
    4. • Check the Fuel Level signal and sensor ground circuits for poor connections/terminal tension at the PCM and at the sensor connector. Refer to Intermittents and Poor Connections Diagnosis .
    • Using DMM J 39200 , check the harness between the PCM and the sensor for high resistance on both circuits.
    • Using DMM J 39200 measure the resistance between the signal circuit and a known good ground. No continuity should be indicated (OL).
    • Using DMM J 39200 measure the resistance between the signal circuit and all other circuits in the PCM connectors and at the fuel tank connector. No continuity should be indicated (OL).

Was a problem found and corrected?

--

System OK

Go to Step 8

6

Check for poor connections/terminal tension at the Fuel Level sensor. Refer to Intermittents and Poor Connections Diagnosis .

Was a problem found and corrected?

--

System OK

Go to Step 7

7

Replace the Fuel Level sensor. Refer to Fuel Sender Assembly Replacement .

Is the action complete?

--

System OK

--

8

Important: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Is the action complete?

--

System OK

--