System Description
The fuel tank pressure (FTP) sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal voltage varies depending on EVAP system pressure or vacuum. The controller uses this FTP signal to determine atmospheric pressure for use in the engine-off small leak test, DTC P0442. Before using this signal as an atmospheric reference it must first be re-zeroed. If the FTP signal is out of range during the re-zero procedure, this DTC will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0451 Fuel Tank Pressure (FTP) Sensor Performance
Conditions for Running the DTC
| • | DTC P0451 runs only when the engine-off natural vacuum small leak test, P0442, executes. |
| • | The number of times this test runs can range from 0-2 per engine-off period. The length of the test can be up to 10 minutes. |
Conditions for Setting the DTC
This DTC will set if the controller is unable to re-zero the FTP sensor voltage within a calibrated range during the engine-off small leak test, P0442.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and DTC with a scan tool. |
Diagnostic Aids
| • | A restriction in the EVAP canister or vent lines could prevent fuel vapor pressure from bleeding off fast enough. If the vent system cannot bleed off pressure fast enough, the re-zero procedure may not complete successfully, which could cause this code to set. By using the purge solenoid command on a scan tool, vacuum can be applied to the system instead of pressure. With the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, the vacuum should not increase to more than 9 inches H2O. |
| • | Ensure that the reference port on the FTP sensor is unobstructed. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 | Inspect the Evaporative Emission (EVAP) System for the following conditions:
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 3 | ||||||
3 |
Is the fuel tank pressure sensor parameter within the specified range? | -1 to +1 in H2O | Go to Step 4 | Go to Step 9 | ||||||
4 |
Important: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
Is the fuel tank pressure sensor parameter less than the second specified value? | 5 in H2O 1 in H2O | Go to Step 5 | Go to Step 7 | ||||||
5 |
Is the difference between the FTP parameter on a scan tool and the VACUUM/PRESSURE gage on the J 41413-200 within the specified value, until the vacuum reached the abort limit on a scan tool? | 1 in H2O | Go to Step 6 | Go to Step 9 | ||||||
6 | Did the FTP parameter on a scan tool display more than the specified value? | 3.2 V | Go to Diagnostic Aids | Go to Step 12 | ||||||
7 | Disconnect the EVAP vent hose from the EVAP canister vent solenoid valve. Is the fuel tank pressure sensor parameter less than the specified value? | 1 in H2O | Go to Step 13 | Go to Step 8 | ||||||
8 | Disconnect the EVAP vent hose from the EVAP canister. Is the fuel tank pressure sensor parameter less than the specified value? | 1 in H2O | Go to Step 11 | Go to Step 14 | ||||||
9 | Test for an intermittent and for a poor connection at the fuel tank pressure (FTP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 10 | ||||||
10 | Test the low reference circuit of the FTP sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 | ||||||
11 | Repair the pinched or restricted EVAP vent hose. Did you complete the repair? | -- | Go to Step 15 | -- | ||||||
12 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
13 | Replace the EVAP canister vent solenoid valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
14 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
15 |
Is the fuel tank pressure sensor parameter within the specified range? | -1 to +1 in H2O | Go to Step 16 | Go to Step 2 | ||||||
16 |
Important: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
Is the fuel tank pressure sensor parameter less than the second specified value? | 5 in H2O 1 in H2O | Go to Step 17 | Go to Step 2 | ||||||
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
