Circuit Description
The primary fuel level sensor and the secondary fuel level sensor changes resistance in response to the fuel level. The powertrain control module (PCM) 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 resistance of both fuel level sensors are high and the PCM senses a high 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 resistance of the fuel level sensors are low and the PCM senses a low signal voltage. The PCM 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 tank. The PCM sends the fuel level percentage 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 lower than normal secondary fuel level sensor signal.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | The secondary fuel level signal is less than 0.5 volts. |
| • | The above condition is present for greater than 20 seconds. |
Action Taken When the DTC Sets
| • | The fuel gage defaults to empty. |
| • | The low fuel indicator illuminates. |
| • | The PCM records the operating conditions at the time that the diagnostic test 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/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 in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View References: Instrument Panel, Gages, and Console Connector End Views , Powertrain Control Module Connector End Views in Engine Controls - 4.3L or Powertrain Control Module Connector End Views in Engine Controls - 4.8L, 5.3L, and 6.0L | ||||||||
1 | Did you perform the Instrument Cluster Diagnostic System Check? | -- | Go to Step 2 | |||||
2 |
Does the scan tool indicate that the Fuel Level Sensor Rear parameter is less than the specified value? | 0.5 V | Go to Step 3 | Go to Diagnostic Aids | ||||
Does the scan tool indicate that the Fuel Level Sensor Rear parameter is greater than the specified value? | 4.5 V | Go to Step 5 | Go to Step 4 | |||||
4 | Test the signal circuit of the secondary fuel level sensor for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 | ||||
5 | Test the signal circuit of the secondary fuel level sensor for a short to ground between C101 and the secondary fuel level sensor. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 | ||||
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 in Wiring Systems. 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 powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 | ||||
8 | Replace the secondary fuel level sensor. Refer to the following:
Did you complete the replacement? | -- | Go to Step 10 | -- | ||||
9 |
Important: Program the replacement PCM. Replace the PCM. Refer to the following:
Did you complete the replacement? | -- | Go to Step 10 | -- | ||||
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||
