The fuel tank pressure (FTP) sensor measures the difference between the air pressure or vacuum in the evaporative emission (EVAP) system and the outside air pressure. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If the FTP sensor signal voltage becomes fixed while driving, or fluctuates more than a calibrated amount at idle, this DTC sets.
The following table illustrates the relationship between the FTP sensor signal voltage and the EVAP system pressure/vacuum.
FTP Sensor Signal Voltage | Fuel Tank Pressure |
---|---|
High, Approximately 1.5 Volts or More | Negative Pressure/Vacuum |
Low, Approximately 1.5 Volts or Less | Positive Pressure |
This diagnostic procedure supports the following DTC:
DTC P0451 Fuel Tank Pressure (FTP) Sensor Performance
• | DTCs P0030, P0031, P0032, P0050, P0051, P0052, P0068, P0101, P0102, P0103, P0111, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0151, P0152, P0153, P0154, P0155, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0221, P0222, P0223, P0261, P0261, P0262, P0264, P0265, P0268, P0270, P0271, P0273, P0274, P0276, P0277, P0279, P0280, P0282, P0283, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0313, P0443, P0446, P0449, P0452, P0453, P0454, P0458, P0459, P0496, P0498, P0499, P0500, P0722, P0723, P1111, P1112, P1114, P1115, P1791, P1795, P2100, P2101, P2108, P2119, P2122, P2123, P2127, P2128, P2135, P2138, P2234 are not set. |
• | The engine is idling. |
• | The FTP has varied at least once before idling. |
OR |
• | The vehicle speed is more than 45 km/h (28 mph). |
• | The canister is purging. |
• | The FTP is more than 0.02 volts. |
• | The FTP varies more than 0.37 mm Hg (0.2 inches H2O) for 5 seconds at idle. |
OR |
• | The FTP varies less than 0.02 volts for 5 seconds while driving. |
• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (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 the DTC with a scan tool. |
Step | Action | Value(s) | Yes | No | ||||||
---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||
2 |
Did DTC P0651 fail this ignition? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 | ||||||
3 |
Is the voltage within the specified value? | 4.9-5.1 V | Go to Step 4 | Go to Step 6 | ||||||
4 |
Is the Fuel Tank Pressure sensor parameter within the specified value? | 4.9-5.1 V | Go to Step 5 | Go to Step 8 | ||||||
5 | Measure the voltage from the 5-volt reference circuit to the low reference circuit with a DMM. Is the voltage within the specified value? | 4.9-5.1 V | Go to Step 9 | Go to Step 7 | ||||||
6 | Test the 5-volt reference circuit for an open circuit or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||
7 | Test the low reference circuit of the FTP sensor for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||
8 | Test the signal circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||
9 | Test for an intermittent and for a poor connection at the FTP 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 13 | Go to Step 11 | ||||||
10 | Test for an intermittent and for a poor connection at the control module. 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 13 | Go to Step 12 | ||||||
11 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||
12 | Replace the engine control module (ECM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||
13 |
Important: DO NOT exceed the specified value in this step. Exceeding this specified value may produce incorrect test results.
Does the fuel tank pressure sensor parameter remain constant? | 5 in H2O | Go to Step 14 | Go to Step 2 | ||||||
14 | Observe the fuel tank pressure sensor parameter with a scan tool. Is the difference between the scan tool fuel tank pressure sensor parameter and the J 41413-200 gage within the specified value? | 1 in H2O | Go to Step 15 | Go to Step 2 | ||||||
15 |
Does the pressure decrease? | -- | Go to Step 16 | Go to Step 2 | ||||||
16 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 17 | ||||||
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |