Circuit Description
The PCM uses a fuel level input from the Body Control Module (BCM) in order to determine if the fuel level is too high or too low in order to be able to accurately detect any EVAP system failures. The fuel level is used to calculate any expected vapor volume within the fuel system. These pressures volume varies as the fuel level changes, so the importance of the pressures is critical in order to determine if the Evaporative Emissions System is operating properly. If a DTC P0461 is set along with an EVAP System DTC, the EVAP DTC cannot be considered valid until you repair and clear DTC P0461.
Conditions for Setting the DTC
Fuel level hasn't changed more than 1.6% in 120 miles.
Action Taken When the DTC Sets
| • | The PCM will record the operating conditions during the time which the diagnostic fails. This information will store in the Failure Records buffer. |
| • | A history DTC stores. |
| • | The fuel level will default to 40 percent. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
If a DTC P0461 is set along with an EVAP System DTC, the EVAP DTC cannot be considered valid until you repair and clear DTC P0461. A DTC U1000 or U1064 set along with a DTC P0461, indicates that the PCM was unable to obtain updated fuel level information due to a serial data communication problem with the Body Control Module (BCM). You must diagnose DTC U1000 or U1064 before DTC P0461, as the only problem may have been the serial communication problem and the vehicle was driven more than 120 miles before the vehicle was brought in for service.
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
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DTC U1000 or U1064 must be diagnosed before DTC P0461 as the only problem may have been the serial communication problem and the vehicle was driven more than 120 miles before the vehicle was brought in for service.
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The fuel level sensor and the BCM are diagnosed in the Computer System Diagnosis portion of the service manual.
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Repair verification is an important step in any diagnostic procedure. Comparing the fuel level readings before and after the repairs is a good way to determine if a repair has been successful.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Was a DTC U1000 or U1064 also set? | -- | Go to applicable DTC table | ||
Refer to the Body Control Module System Check portion of the service manual. Is the action complete? | -- | -- | ||
Verify the repairs by viewing the scan tool fuel level data. Does the fuel level data reflect the correct amount of fuel in the tank? | -- | |||
5 |
Does the scan tool indicate that this diagnostic has ran and passed? | -- | ||
6 | Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
