Circuit Description
The primary fuel level sender and the secondary fuel level sender change resistance in response to the fuel level. The engine control module (ECM) 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 resistances of both fuel level senders are high, and the ECM 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 resistances of the fuel level senders are low, and the ECM senses a low signal voltage. The ECM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via the class 2 serial data circuit to the instrument panel cluster (IPC) in order to control the fuel gage.
This diagnostic tests for a higher than normal secondary fuel level sender signal.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1433 Fuel Level Sensor 2 Circuit High Voltage
Conditions for Running the DTC
The engine is running (LG4).
Conditions for Setting the DTC
| • | The secondary fuel level signal is greater than 98 percent (LG4). |
| • | 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 in Wiring Systems. |
| • | When the secondary fuel level sensor signal is higher than normal, the Fuel Level Sensor percent parameter in the ECM Fuel System 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 | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehiclein Vehicle DTC Information |
2 |
Does the scan tool indicate that the Fuel Level Sensor percent parameter is greater than the specified value? | 98% | Go to Step 3 | Go to Diagnostic Aids |
Does the scan tool indicate that the Fuel Level Sensor percent parameter is less than the specified value? | 50% | Go to Step 6 | Go to Step 4 | |
4 | Test the signal circuit of the secondary fuel level sensor 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 10 | Go to Step 5 |
5 | Test the low reference circuit of the secondary fuel level sensor for an open, a high resistance, or a short to voltage. Refer to Circuit Testing and Wiring Repairsin Wiring Systems. 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 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 ECM. 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 10 | Go to Step 9 |
8 | Replace the secondary fuel level sensor. Refer to Fuel Sender Assembly Replacement in Engine Controls - 7.8L. Did you complete the replacement? | -- | Go to Step 10 | -- |
9 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems 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 |
