DTC P2068 4.8L, 6.0L, and 8.1L Engines
Circuit Description
The primary fuel level sender and the secondary fuel level sender changes resistance based on fuel level. 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 the fuel level. When the fuel tanks are full, the resistance of both fuel level senders are low and the PCM 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 resistance of the fuel level senders are high and the PCM senses a high signal voltage. The PCM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the percentage of the remaining fuel in the tank. The PCM sends the fuel level percent via the class 2 serial data circuit to the instrument cluster in order to control the fuel gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.
This diagnostic tests for a higher than normal secondary fuel level sender signal.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | The secondary sender output is greater than 2.9 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 PCM records the operating conditions at the time the diagnostic fails. The PCM 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 PCM receives the clear code command from the scan tool. |
Diagnostic Aids
Use the Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data may aid in determining the number of miles since the DTC set. The Fail Counter and Pass Counter can also aid in determining the number of ignition cycles that the diagnostic reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature, etc.). This will isolate when the DTC failed.
Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | ||||||||
1 | Did you perform the Instrument Cluster Diagnostic System Check? | -- | Go to Step 2 | |||||
2 |
Does the scan tool indicate that the Fuel Tank Level Remaining % parameter is less than the specified value? | 4% | Go to Step 3 | Go to Diagnostic Aids | ||||
Does the scan tool indicate that the Fuel Tank Level Remaining % parameter is greater than the specified value? | 98% | Go to Step 6 | Go to Step 4 | |||||
4 | Test the signal circuit of the fuel level sender for an open, a high resistance, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 5 | ||||
5 | Test the low reference circuit of the fuel level sender for an open, a high resistance, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||
6 | Test the signal circuit of the fuel level sender for an open, a high resistance, or a short to voltage between C152 and the fuel level sender. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 | ||||
7 | Test the low reference circuit of the fuel level sender for an open, a high resistance, or a short to voltage between C152 and the fuel level sender. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 | ||||
8 | Inspect for poor connections at the harness connector of the fuel level sender. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||
9 | Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||
10 | Replace the fuel level sender. Refer to the following procedures:
Did you complete the replacement? | -- | Go to Step 12 | -- | ||||
11 |
Important: Program the replacement PCM. Replace the PCM. Refer to the following procedures:
Did you complete the replacement? | -- | Go to Step 12 | -- | ||||
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||
DTC P2068 5.3L Engine
Circuit Description
The primary fuel level sender and the secondary fuel level sender changes resistance based on fuel level. 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 the fuel level. When the fuel tanks are full, the resistance of both fuel level senders are high and the PCM senses a high 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 resistance of the fuel level senders are low and the PCM senses a low signal voltage. The PCM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the percentage of the remaining fuel in the tank. The PCM sends the fuel level percent via the class 2 serial data circuit to the instrument cluster in order to control the fuel gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.
This diagnostic tests for a higher than normal secondary fuel level sender signal.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | The secondary sender output is greater than 2.9 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 PCM records the operating conditions at the time the diagnostic fails. The PCM 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 PCM receives the clear code command from the scan tool. |
Diagnostic Aids
Use the Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data may aid in determining the number of miles since the DTC set. The Fail Counter and Pass Counter can also aid in determining the number of ignition cycles that the diagnostic reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature, etc.). This will isolate when the DTC failed.
Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | ||||||||
1 | Did you perform the Instrument Cluster Diagnostic System Check? | -- | Go to Step 2 | |||||
2 |
Does the scan tool indicate that the Fuel Tank Level Remaining % parameter is greater than the specified value? | 98% | Go to Step 3 | Go to Diagnostic Aids | ||||
Does the scan tool indicate that the Fuel Tank Level Remaining % parameter is less than the specified value? | 4% | Go to Step 6 | Go to Step 4 | |||||
4 | Test the signal circuit of the fuel level sender for an open, a high resistance, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 5 | ||||
5 | Test the low reference circuit of the fuel level sender for an open, a high resistance, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||
6 | Test the signal circuit of the fuel level sender for an open, a high resistance, or a short to voltage between C152 and the fuel level sender. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 | ||||
7 | Test the low reference circuit of the fuel level sender for an open, a high resistance, or a short to voltage between C152 and the fuel level sender. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 | ||||
8 | Inspect for poor connections at the harness connector of the fuel level sender. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||
9 | Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||
10 | Replace the fuel level sender. Refer to the following procedures:
Did you complete the replacement? | -- | Go to Step 12 | -- | ||||
11 |
Important: Program the replacement PCM. Replace the PCM. Refer to the following procedures:
Did you complete the replacement? | -- | Go to Step 12 | -- | ||||
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||
