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 VoltageDiagnostic 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, evaporative emission (EVAP), and other onboard 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. |
Reference Information
Schematic Reference
| • | Engine Controls Schematics for the 4.3L engine |
| • | Engine Controls Schematics for the 4.8L, 5.3L, 6.0L, and 6.2L engines |
| • | Engine Controls Schematics for the 6.6L engine |
Connector End View Reference
| • | Engine Controls Connector End Views for the 4.3L engine |
| • | Engine Control Module Connector End Views for the 4.8L, 5.3L, 6.0L, and 6.2L engines |
| • | Engine Control Module Connector End Views for the 6.6L engine |
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Ignition ON, observe the scan tool Fuel Tank Level Remaining parameter. The reading should be between 4-98 percent.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the secondary fuel level sensor.
- Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit and ground.
- 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.
- If all circuits test normal, test or replace the secondary fuel level sensor.
| ⇒ | If greater than 1 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Fuel Level Sensor Replacement for the 4.3L engine |
| • | Fuel Level Sensor Replacement for the 4.8L, 5.3L, 6.0L, and 6.2L engines |
| • | Fuel Level Sensor Replacement for the 6.6L engine |
| • | Control Module References for the ECM replacement, setup, and programming |
