P2068

DTC P2068

DTC Descriptor

DTC P2068
- Fuel Level Sensor 2 Circuit High Voltage

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview






Circuit/System Description

The secondary (right) fuel level sender changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the secondary (right) fuel level sender in order to determine the fuel level. When the fuel tank is full, the secondary (right) fuel level sender resistance is high and the ECM senses a high signal voltage. When the fuel tank is empty, the secondary (right) fuel level sender resistance is low and the ECM senses a low signal voltage. The ECM uses the signal circuit of the secondary (right) fuel level sender in order to calculate the percentage of remaining fuel in the secondary tank. The ECM sends the fuel level information via GMLAN serial data circuit to the instrument panel cluster (IPC) for display in 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.
* The system voltage is between 9-16 volts.

Conditions for Setting the DTC

* The secondary (right) fuel level sensor voltage is greater than 4.5 volts.
* The above condition is present for greater than 6 seconds.

Action Taken When the DTC Sets

* The fuel gage defaults to empty.
* The driver information center (DIC) displays the FUEL LEVEL LOW message.
* 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

With the scan tool installed and the ignition ON, the Fuel Level Sensor Right Tank parameter in the ECM EVAP Data List indicates a value at or greater than 4.5 volts.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the secondary (right) fuel level sensor.
2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit and ground.

• If greater than 1 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuits tests normal, replace the ECM.

3. Install a 3-A fused jumper wire between the signal circuit and the low reference circuit of the secondary (right) fuel level sensor. With the scan tool, observe the Fuel Level Sensor Right Tank parameter and verify the parameter is less than 0.5 volts.

• If greater than 0.5 volts, test the secondary (right) fuel level sensor signal and low reference circuits for a short to voltage or an open/high resistance. If the circuits test normal, replace the ECM.

4. If all circuits tests normal, test or replace the fuel level sensor.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Fuel Level Sensor Replacement - Left Side for the 6.0L engine
* Fuel Level Sensor Replacement - Left Side for the 7.0L engine
* Refer to Programming and Relearning.Programming and Relearning