Circuit Description
The PCM requires an accurate indictation of fuel level for EVAP system diagnosis. The fuel level in the fuel tank changes the rate of vacuum decay for the EVAP system leak DTC's.
The Fuel Level Sensor changes resistance based on fuel level. The Fuel Level Sensor has a signal circuit and a ground circuit. The IPC applies a voltage (about 12 volts) on the signal circuit to the sensor. The IPC monitors changes in this voltage caused by changes in the resistance of the sensor to determine fuel level.
When the fuel tank is full, the sensor resistance is high, and the IPC's signal voltage is only pulled down a small amount through the sensor to ground. Therefore, the IPC will sense a high signal voltage (fuel tank full). When the fuel tank is empty, the sensor resistance is low, and the signal voltage is pulled down a greater amount. This causes the IPC to sense a low signal voltage (fuel tank empty).
The IPC uses inputs from the Fuel Level Sensor to calculate the fuel level in the fuel tank. This information is then sent to the PCM through Serial Data.
When the PCM senses a signal voltage higher than the normal operating range of the sensor, this DTC sets.
Conditions for Running the DTC
| • | DTC P0601 is not set. |
| • | Vehicle speed is more than 5 km/h. |
Conditions for Setting the DTC
The fuel level sensor voltage goes above normal operating range for a specific length of time.
Action Taken When the DTC Sets
The PCM uses a fuel remaining value of 40% for the EVAP system diagnostic tests.
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | No message will be displayed. |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in Powertrain Control Module Description . |
Diagnostic Aids
Important: Fuel level is used to determine EVAP system diagnosis. Always diagnose the fuel level sensor before any other EVAP system components or DTC's.
Refer to Body Electrical for fuel level sensor diagnosis. Check for IPC DTC's.
Do not use the fuel gauge as an indication of a shorted or open circuit as the IPC may always default to EMPTY or FULL depending upon vehicle model.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Refer to Diagnostic Aids |
