Fuel Gauge Inoperative or Inaccurate

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The IPC monitors the fuel level sender in the fuel tank, divides this voltage by the Ignition 1 reference voltage (1D50), and looks up the corresponding fuel level in a table to determine actual fuel level (1D40). This value is then filtered (to account for slosh and minor variations) and displayed on the IPC. A control feature is included which allows the fuel display to bypass the filtering feature if there is a rapid increase in fuel level (i.e. vehicle is being refueled).

Normal Operation Digital:

Fuel level is displayed as the filtered fuel level in whole gallons (liter). When the IPC reads above 18.9 gallons the display will read "F". Readings between 18.9 and 2.0 gallons will be displayed as whole gallon numbers. When the level reaches 2.0 gallons the display will read "E". When the level reaches 1.0 gallons the "E" will flash and a "Fuel Level Very Low" message will appear on the DIC.

Normal Operation Analog:

Fuel level is displayed as the filtered fuel level as a digital display. When the level reaches 1.0 gallons a "Fuel Level Very Low" message will appear on the DIC.

Display Off Warning:

If the vehicle is operating in "Display Off" mode and the fuel level falls below 4 gallons, all displays will return to active mode and the DIC will display "CHECK FUEL GAGE".

Non-Linear or Erratic Operation:

Ensure good terminal contact at all electrical connection. Hand operate fuel level sending unit through complete range of travel watching for jumps or irregularities in value of 1D40. Ensure free travel and proper clearance for sending unit float. When monitoring performance, always use ID4O instead of gage to eliminate slow filtering of level.

TEST DESCRIPTION

Test numbers refer to circled numbers on the diagnostic chart.

1. If the IPC sees low battery voltage (indicated by I041), the fuel gage reference will be lost and low or intermittently low fuel will be displayed.

2. If the IPC loses ignition 1 input, it has no reference for fuel level voltage and will display empty on the gage.

3. Always full indicates the IPC is always receiving closes to system voltage from the fuel level sender.

4. If the radio continues to play, the Retained Accessory Power (RAP) module is receiving power and therefor CKT 139 is powered to at least splice S402.

5. Jumpering Cavities "D" to "E" should force the 1D40 (Fuel Level) to read full.