P2068
DTC P2068
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC P2068
- Fuel Level Sensor 2 High Voltage
Diagnostic Fault Information
Circuit/System Description
The primary fuel level sensor and the secondary fuel level sensor change resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the primary fuel level sensor, the secondary fuel level sensor, and the type of fuel in order to determine the fuel level. For regular unleaded fuel the ECM monitors a constant signal. When the vehicle has approximately 20% or greater ethanol for E85 fuel applications, the ECM controls a pulse cycle signal where it monitors the signal and calculates the fuel level percentage only during the on pulse of approximately 100 ms.
When the fuel tanks are full, the sensor resistances of both fuel level sensors are low and the ECM senses a low signal voltage on both the signal circuits of the primary fuel level sensor and 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 circuit of the primary fuel level sensor and the secondary fuel level sensor in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via the serial data circuit to the instrument cluster in order to control the fuel gauge.
Conditions for Running the DTC
* The ignition is ON, with the engine running.
* The system voltage is between 9-16 V.
Conditions for Setting the DTC
* The secondary sensor output is greater than 3.5 V.
* The above condition is present for greater than 30 seconds.
Action Taken When the DTC Sets
* The fuel gauge 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.
Reference Information
Schematic Reference
Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Instrument Cluster Description and Operation (Instrument Cluster)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Control Module References) for scan tool information
Circuit/System Verification
Ignition ON, verify the scan tool Fuel Tank Level Remaining parameter is between 4-98 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 ohm between the low reference circuit terminal B and ground.
• If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition ON, install a 3 A fused jumper wire between the secondary signal circuit terminal C and the low reference circuit terminal B. Verify the scan tool Fuel Tank Level Remaining parameter display is greater than 98 percent.
• If less than the specified range, test the secondary signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
4. If all circuits test normal, test or replace the secondary fuel level sensor.
Component Testing
1. Ignition OFF, remove the secondary fuel level sender.
2. While sweeping the fuel level sensor through its full range of motion, test for a minimum resistance value of less than 41 ohm and a maximum value greater than 119 ohm between the secondary signal terminal B and the low reference terminal C.
• If not within the specified range, replace the secondary fuel level sensor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Fuel Level Sensor Replacement (Regular Cab w/26 Gal Tank) ()Fuel Level Sensor Replacement (Extended Cab w/26 Gal Tank) ()Fuel Level Sensor Replacement (Regular Cab w/34 Gal Tank) () for the 4.3L engine
* Fuel Level Sensor Replacement (15 Reg Cab With 26 gal Tank) (Fuel Level Sensor Replacement (15 Reg Cab With 26 gal Tank))Fuel Level Sensor Replacement (15 Ext/Crew Cab With 26 gal Tank) (Fuel Level Sensor Replacement (15 Ext/Crew Cab With 26 gal Tank))Fuel Level Sensor Replacement (15 Reg/Ext/Crew Cab w/34 gal Tank) (Fuel Level Sensor Replacement (15 Reg/Ext/Crew Cab w/34 gal Tank))Fuel Level Sensor Replacement (25 Ext/Crew Cab w/26 gal Tank) (Fuel Level Sensor Replacement (25 Ext/Crew Cab w/26 Gal Tank)) for the 4.8L, 5.3L, 6.0L, and 6.2L engines
* Fuel Level Sensor Replacement () for the 6.6L engine
* Control Module References (Control Module References) for ECM replacement, programming and setup