GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

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

DTC Descriptor

DTC P2068: Fuel Level Sensor 2 High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Fuel Level Sensor Reference Voltage Circuit

P2067

--

--

P2066

Fuel Level Sensor Signal Circuit

P2067

P2068

1

P2068

P2066

Fuel Level Sensor Low Reference Circuit

--

P2068

1

P2068

P2066

1. Fuel Gage Inaccurate or Inoperative

Circuit/System Description

The primary fuel level sender and the secondary fuel level sender changes resistance based on fuel level. The engine control module (ECM) monitors the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to determine the fuel level. When the fuel tank is full, the resistances of both fuel level senders are low and the ECM senses a low signal voltage on both the signal circuits of the primary fuel level sender and the secondary fuel level sender. When the fuel tanks are empty, the resistances of the fuel level senders are high and the ECM senses a high signal voltage. The ECM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via GMLAN serial data circuit to the instrument cluster in order to control the fuel gage. The fuel information is also used for misfire and evaporative emission (EVAP) diagnostics.

Conditions for Running the DTC

    • The ignition is ON, with the engine running.
    • The system voltage is between 9-16 volts.

Conditions for Setting the DTC

    • The secondary sensor output is greater than 3.5 volts.
    • The above condition is present for greater than 30 seconds.

Action Taken When the DTC Sets

    • The fuel gage defaults to empty.
    • The low fuel indicator illuminates.
    • The ECM records the operating conditions at the time that the diagnostic test fails. The ECM displays the failure information in the Failure Records on the scan tool

Conditions for Clearing the DTC

    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction-free warm-up cycles.
    • The ECM receives a clear code command from the scan tool.

Circuit/System Verification

Ignition ON, observe the scan tool Fuel Tank Level Remaining parameter. The reading should be between 4 percent and 98 percent.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the secondary fuel level sensor.
  2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit and ground.
  3. If greater than 1.0 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition ON, install a 3-amp fused jumper between and secondary signal circuit and the low reference circuit. Verify the scan tool Fuel Tank Level Remaining parameter is greater than 98 percent.
  5. If less than 98 percent, test the secondary signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. If all circuits test normal, test or replace the secondary fuel level sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Engine Control Module Replacement for the 2.0L diesel engine.
    •  Engine Control Module Replacement for the 2.4L engine.
    •  Control Module References for the ECM replacement, setup, and programming.