GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Savana (CNG) 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 Fuel Indicator Lamp Inoperative - Alternative Fuels

Circuit Description

The fuel gage select switch assembly serves 2  purposes. The fuel gage select switch is used to indicate to the Alternative Fuels ECM that the operator of the vehicle has requested that the fuel gage display the level of fuel for the DORMANT or non-operating fuel system. The fuel indicator lamp (FIL) is used by the Alternative Fuels ECM to indicate to the operator of the vehicle which fuel system is in use. When illuminated the vehicle is operating on gasoline.

The fuel indicator lamp (FIL) is supplied power by the Alternative Fuels ECM and the ground path is supplied through the alternative fuel engine harness ground. The Alternative Fuels ECM will supply power to the FIL for a 2 second bulb check at ignition ON during CNG operation or continuously during gasoline operation when the ignition is in the ON or RUN positions.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The System Check MUST be performed before proceeding with this diagnostic table. Failure to perform the System Check will result in mis-diagnosis.

    2.

  2. This step checks for proper operation of the FIL.

    3.

  3. The FIL should only stay illuminated when the engine is operating on gasoline.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Were you sent here from other diagnostic service information?

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2

  1. Turn the ignition OFF and wait 30 seconds.
  2. Observe the fuel indicator lamp (FIL) located in the fuel gage select switch button.
  3. Turn the ignition ON leaving the engine OFF.

Did the FIL illuminate for a 2 second bulb check and then go OFF?

Go to Step 3

Go to Step 4

3

  1. Start and idle the engine.
  2. Observe the fuel indicator lamp (FIL) located in the fuel gage select switch button.

Is the fuel indicator lamp illuminated while the engine is running?

Go to Fuel Indicator Lamp Always On - Alternative Fuels

System OK

4
  1. Remove the fuel gage select switch from the instrument panel.
  2. Disconnect the fuel gage select switch connector.
  3. Connect the J 35616-200 Un-powered Test Lamp between BATTERY POSITIVE and the switch GROUND circuit terminal .

Is the test lamp illuminated?

Go to Step 5

Go to Step 7

5
  1. Connect the J 35616-200 between the switch GROUND circuit terminal and the Fuel Indicator Control circuit terminal.
  2. Observe the test lamp as you turn the ignition ON while leaving the engine OFF.

Did the test lamp illuminate for at least a 2 second bulb check?

Go to Step 8

Go to Step 6

6
  1. Turn the ignition OFF and wait 30 seconds.
  2. Disconnect the Alternative Fuels ECM connectors.
  3. Check the Fuel Indicator Control circuit for continuity between the Alternative Fuels ECM connector terminal and the fuel gage select switch connector terminal.
  4. Check the Fuel Indicator Control circuit for a short to ground.
  5. Check for proper terminal contact at the Alternative Fuels ECM and the switch connectors.
  6. Repair wiring or terminals as necessary.

Was a wiring or terminal repair necessary?

Go to Step 10

Go to Step 9

7

Repair the open fuel gage select switch ground circuit.

Is the repair complete?

Go to Step 10

--

8

Replace the fuel gage select switch assembly.

Is the replacement complete?

Go to Step 10

--

9
  1. Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .
  2. Program the replacement control module with the correct vehicle software and calibration.

Is the replacement complete?

Go to Step 10

--

10
  1. Remove all test equipment except the scan tool.
  2. Connect any disconnected components, fuses, etc.
  3. Using a scan tool clear DTC Information from the Alternative Fuels ECM and the gasoline control module (VCM/PCM or ECM).
  4. Turn the ignition OFF and wait 30 seconds.
  5. Start the engine and operate the vehicle.
  6. Observe the fuel indicator lamp and the MIL.
  7. Observe vehicle performance and driveability.
  8. After operating the vehicle inspect BOTH control modules for stored DTCs.

Does the vehicle operate on CNG with normal driveability, no FIL/MIL illumination and no stored DTCs?

System OK

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)