DTC P2068 3.6 (LY7)
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 | P2068¹ | P2068 | P2066 |
Fuel Level Sensor Low Reference Circuit | -- | P2068¹ | P2068 | P2066 |
¹Fuel Gage inaccurate or Inoperative | ||||
Circuit/System Description
The primary fuel level sensor and the secondary fuel level sensor change resistance in response to fuel level. The engine control module (ECM) monitors the signal circuit of the primary fuel level sensor and the secondary fuel level sensor in order to determine the fuel level. When the fuel tanks are full, the resistances of both fuel level sensors are low, and the ECM senses a low signal voltage on both the signal circuit of the primary fuel level sensor and the signal circuit of the secondary fuel level sensor. When the fuel tanks are empty, the resistances of the fuel level sensors are high, and the ECM senses a high signal voltage. The ECM uses the signal circuits of the primary fuel level sensor and the secondary fuel level sensor in order to calculate the percentage of remaining fuel in the tanks. The ECM sends the fuel level percentage via the 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 on-board diagnostics.
Conditions for Running the DTC
| • | The engine keeps running. |
| • | The system voltage is between 10.5-18 volts. |
| • | The DTC P2068 runs continuously once the above condition is present. |
Conditions for Setting the DTC
| • | The secondary fuel level signal is greater then 3.2 volts. |
| • | The above condition is present for 4 minutes. |
Action Taken When the DTC Sets
| • | The fuel gage defaults to empty. |
| • | The driver information center (DIC) illuminates the FUEL LEVEL LOW message. |
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnosis runs and fails. |
| • | The control module records the operating conditions at the time of the diagnostic failure. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the DTC
| • | The control module turns OFF the MIL after 4 consecutive ignition cycles that the diagnosis runs and does not fail. |
| • | A current DTC, Last Test Failed, is cleared when the diagnosis runs and passes. |
| • | A history DTC is cleared after 10 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnosis. |
| • | Clear the MIL and the DTC with a scan tool. |
Reference Information
Fuel Level Specifications
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
With the scan tool installed and the ignition ON, the Fuel Tank Level Remaining parameter in the ECM EVAP Data List indicates a value at or greater than 4.9 volts.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the secondary fuel level sensor.
- Ignition OFF, test for less than 1 ohm between the ground reference circuit and ground.
- Ignition ON, install a 3-amp fused jumper wire between the secondary signal circuit and the low reference circuit. Verify if the Fuel Tank Level Remaining parameter of the scan tool is greater than 4.9 volts.
- If all circuits test normal, test or replace the secondary fuel level sensor.
| ⇒ | If the parameter is 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 the parameter is less than 4.8 volts, 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.
| • | Control Module References for the ECM replacement, setup, and programming |
DTC P2068 4.6L (LH2)
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 | P2068¹ | P2068 | P2066 |
Fuel Level Sensor Low Reference Circuit | -- | P2068¹ | P2068 | P2066 |
¹Fuel Gage Inaccurate or Inoperative | ||||
Circuit/System Description
The primary fuel level sensor and the secondary fuel level sensor change resistance in response to fuel level. The engine control module (ECM) monitors the signal circuit of the primary fuel level sensor and the secondary fuel level sensor in order to determine the fuel level. When the fuel tanks are full, the resistances of both fuel level sensors are low, and the ECM senses a low signal voltage on both the signal circuit of the primary fuel level sensor and the signal circuit of the secondary fuel level sensor. When the fuel tanks are empty, the resistances of the fuel level sensors are high, and the ECM senses a high signal voltage. The ECM uses the signal circuits of the primary fuel level sensor and the secondary fuel level sensor in order to calculate the percentage of remaining fuel in the tanks. The ECM sends the fuel level percentage via the 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 on-board diagnostics.
Conditions for Running the DTC
DTC P2068 runs continuously.
Conditions for Setting the DTC
The primary fuel level sensor signal voltage is greater than 3.5 volts.
Action Taken When the DTC Sets
| • | The fuel gage defaults to empty. |
| • | The driver information center (DIC) illuminates the FUEL LEVEL LOW message. |
| • | DTC P2068 is a type B DTC. |
Conditions for Clearing the DTC
DTC P2068 is a type B DTC.
Reference Information
Fuel Level Specifications
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
With the scan tool installed and the ignition ON, verify that the Fuel Tank Level Remaining parameter in the ECM EVAP Data List indicates a value at or greater than 0.2 volt.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the secondary fuel level sensor.
- Ignition OFF, test for less than 1 ohm between the ground reference circuit and ground.
- Ignition ON, install a 3-amp fused jumper wire between the secondary signal circuit and the low reference circuit. Verify that the Fuel Tank Level Remaining parameter of the scan tool is greater than 4.9 volts.
- If all circuits test normal, test or replace the secondary fuel level sensor.
| ⇒ | If the parameter is 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 the parameter is less than 4.9 volts, 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.
| • | Control Module References for ECM replacement, setup and programming |
