Circuit Description
The fuel tank pressure sensor responds to changes in the fuel tank pressure or vacuum. The fuel tank pressure sensor signal voltage to the powertrain control module (PCM) varies from more than 4 volts with pressure in the fuel tank, to a minimum of 0.6 volts with a high vacuum condition in the fuel tank.
Conditions for Running the DTC
| • | The barometric pressure (BARO) is more than 75 kPa. |
| • | The intake air temperature is between -8°C and +40°C (18°F-104°F). |
| • | The engine coolant temperature is between -8°C and +110°C (18°F-230°F). |
| • | The engine is running. |
Conditions for Setting the DTC
The voltage is less than 0.5 volts for a specified time.
OR:
The voltage is more than 4.5 volts for a specified time.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns off after 3 consecutively passing trips without a fault present. |
| • | A history DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool Clear DTC Information function. |
Diagnostic Aids
Check for any of the following conditions:
| • | A plugged sensor air vent hole. Inspect the sensor and clean if necessary. |
| • | If multiple DTCs are set, it may be possible to have an open or a shorted reference voltage circuit or an open ground circuit. |
If a DTC P0450 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0450 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0450 appears in the Not Ran Since Code Cleared list, the P0450 diagnostic has not yet run. When the DTC P0450 does not appear in the Not Ran Since Code Cleared list, the P0450 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the P0450 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.
An intermittent malfunction may be caused by a fault in the fuel tank pressure sensor circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Any backed-out terminals |
| • | Any improper mating of terminals |
| • | Any broken electrical connector locks |
| • | Any improperly formed or damaged terminals |
| • | Any faulty terminal-to-wire connections |
| • | Any physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Any corrosion of the electrical connections, the splices, or the terminals |
If the DTC P0450 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
-
Determine if a fault is present. Review the Freeze Frame data to determine the conditions when the DTC set. Always record this information.
-
This step verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes. This also checks the sensor signal input circuit.
-
This step checks the operation of the fuel tank pressure (FTP) control valve.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the pressure within the specified range? | 0.0-0.9 mm Hg (0.0-0.5 in. H2O) | |||
3 |
Was any problem found? | -- | ||
4 |
Does the voltage equal the specified value? | 5.0 V | ||
5 |
Was a repair necessary? | -- | ||
6 | Probe the terminal 2 of the FTP sensor connector on the harness side using a test lamp connected to B+. Does the test lamp illuminate? | -- | ||
7 |
Was a repair necessary? | -- | ||
8 |
Is the voltage within the specified range? | 2.0 - 2.7 V | ||
Apply a small amount of vacuum to the FTP sensor while observing the DMM. Does the voltage decrease when the vacuum is applied? | -- | |||
10 |
Was a repair necessary? | -- | ||
|
Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury. Important: There will be some resistance, but air should flow steadily.
Does air flow through the valve to the tank port side? | -- | |||
12 |
Important: The FTP control valve will not allow air to flow from the tank side port to the canister side port until the pressure on the tank side is more than 3.5 kPa (0.5 psi).
Does the FTP control valve pass both checks? | 15 in Hg | Go to Diagnostic Aids | |
13 | Clean the sensor orifice. Is the action complete? | -- | -- | |
14 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
15 |
Was a repair necessary? | -- | ||
16 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the action complete? | -- | -- | |
17 | Replace the FTP control valve. Refer to Fuel Tank Pressure Control Valve Replacement . Is the action complete? | -- | -- | |
18 |
Are any DTCs displayed on the scan tool? | -- | System OK |
