GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2007 🢒 Ascender - 2WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Fuel Gage Inaccurate or Inoperative

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit Description

The engine control module (ECM)/powertrain control module (PCM) monitors the signal circuit of the fuel level sender in order to determine fuel level. The sender consists of a variable resistor that changes resistance based on the fuel level in the tank. The ECM/PCM monitors the voltage across the sender resistance in order to determine the fuel level. The ECM/PCM uses the signal circuit of the fuel level sender in order to calculate the total remaining fuel, in percent. The ECM/PCM sends the fuel level percent via the serial data circuit to the instrument cluster in order to control the fuel gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.

Reference Information

Schematic Reference

    •  Instrument Cluster Schematics
    •  Engine Controls Schematics for the 4.2L engine
    •  Engine Controls Schematics for the 5.3L engine
    •  Engine Controls Schematics for the 6.0L engine

Connector End View Reference

    •  Displays and Gages Connector End Views
    •  Powertrain Control Module Connector End Views for the 4.2L engine
    •  Engine Control Module Connector End Views for the 5.3L engine
    •  Engine Control Module Connector End Views for the 6.0L engine

Description and Operation

    •  Instrument Cluster Description and Operation
    •  Fuel System Description for the 4.2L engine
    •  Fuel System Description for the 5.3L engine
    •  Fuel System Description for the 6.0L engine

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connectors at the fuel level sensor.
  2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal and ground.
    3. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM/PCM.
  3. Install a Signal Generator and Instrument Panel Tester between the signal circuit terminal and ground.
  4. Ignition ON, vary the signal generator resistance between 40 and 250 ohms. Verify that the scan tool Fuel Tank Level Remaining parameter of the Fuel Level Sensor parameter displays a range that varies between 5 and 95 percent as the signal generator resistance changes.
    5. ⇒If not displaying the specified range, test the signal circuit for an open/high resistance. If the circuits test normal, replace the ECM/PCM.
  5. Vary the signal generator resistance between 40 and 250 ohms. Verify that the fuel gage displays a range that varies between empty and full as the signal generator resistance changes.
    6. ⇒If not displaying the specified range, replace the IPC.
  6. If all circuits test normal, test or replace the fuel level sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Fuel Level Sensor Replacement for the 4.2L engine
    •  Fuel Level Sensor Replacement for the 5.3L engine
    •  Fuel Level Sensor Replacement for the 6.0L engine
    •  Control Module References for the ECM/PCM or IPC replacement, setup, and programming