Circuit Description
The powertrain control module (PCM) monitors the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to determine fuel level. Each sender consists of a variable resistor that changes resistance based on fuel level in both tanks. The PCM monitors the voltage across both sender resistances in order to determine the fuel level. The PCM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the total remaining fuel, in percent. The PCM sends the fuel level percent via serial data circuit to the instrument cluster in order to control the gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2068 Fuel Level Sensor 2 Circuit High Voltage
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The engine is running (LG4). |
Conditions for Setting the DTC
| • | The secondary fuel level signal is greater than 4.5 volts. |
| • | The above condition is present for greater than 20 seconds. |
Action Taken When the DTC Sets
| • | The fuel gage defaults to empty. |
| • | 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 the clear code command from the scan tool. |
Diagnostic Aids
| • | Use the Freeze Frame/Failure Records data in order to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data may help in determining the number of miles since the DTC set. The Fail Counter and Pass Counter can also help in determining the number of ignition cycles that the diagnostic test reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions, including those for RPM, for engine load, for vehicle speed, for temperature, and for others. This will isolate at what point the DTC failed. Refer to Testing for Intermittent Conditions and Poor Connections . |
| • | When the primary fuel level sensor signal is higher than normal, the Fuel Level Sensor Rear Tank % parameter in the ECM Fuel Data data list on the scan tool indicates a value of about 100 percent. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View Reference: Master Electrical Component List | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||
2 |
Does the scan tool indicate that the Fuel Level Sensor Rear Tank parameter is greater than the specified value? | 4.5 V | Go to Step 3 | Go to Diagnostic Aids | ||||||||
Does the scan tool indicate that the Fuel Level Sensor Rear Tank parameter is less than the specified value? | 0.5 V | Go to Step 6 | Go to Step 4 | |||||||||
4 | Test the signal circuit of the secondary fuel level sensor for an open, for a high resistance, or for a short to voltage. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 5 | ||||||||
5 | Test the low reference circuit of the secondary fuel level sensor for an open, for a high resistance, or for a short to voltage. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 | ||||||||
6 | Inspect for poor connections at the harness connector of the secondary fuel level sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 | ||||||||
7 | Inspect for poor connections at the harness connector of the ECM . Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 | ||||||||
8 | Replace the secondary fuel level sensor. Refer to one of the following procedures:
Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||||
9 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||||
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||||
