Circuit Description
The fuel tank pressure sensor responds to changes in fuel tank pressure or vacuum. The fuel tank pressure sensor signal voltage to the powertrain control module (PCM) varies from above 4 volts, with pressure in the fuel tank, to a minimum of 0.6 volts with a high vacuum condition in the fuel tank (vent solenoid closed).
Conditions for Setting the DTC
Input range check:
| • | Voltage is less than 0.5 volts |
| • | Voltage is more than 4.8 volts |
| • | Condition is present for 0.5 seconds |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive drive cycles without a fault present. |
| • | A DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | The DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed. |
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 shorted reference voltage circuit or an open ground circuit. |
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:
| • | Backed out terminals |
| • | Improper mating of terminals |
| • | Broken electrical connector locks |
| • | Improperly formed or damaged terminals |
| • | Faulty terminal to wire connections |
| • | Physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Corrosion of electrical connections, splices, or terminals |
If the 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. 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.
If you cannot duplicate the DTC P0450, 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.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and the 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.
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This step determines if a fault is present. Review the Freeze Frame data in order to determine the condition of when the DTC set. Always record this information.
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This step verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes. This also checks the sensor signal input circuit.
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This step checks the operation of the tank pressure control valve. .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the scan tool display within the specified value? | 0.0-0.9 mm Hg (0.0-0.5 in Hg) | |||
3 |
Did you find any problems? | -- | ||
4 |
Is the voltage at specified value? | 5.0 volts | ||
5 |
Was a repair necessary? | -- | ||
6 | Probe terminal 2 of the fuel tank pressure sensor (harness side), using a test lamp connected to B+. Did the test lamp illuminate? | -- | ||
7 |
Was a repair necessary? | -- | ||
8 |
Was the voltage measured within the specified value? | 2.0 to 2.7 volts | ||
Apply a small amount of vacuum to the fuel tank pressure sensor while observing the DMM. Did the voltage drop when the vacuum was applied? | -- | |||
10 |
Was a repair necessary? | -- | ||
11 |
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? | -- | ||
|
Important: The fuel tank pressure 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 fuel tank pressure control valve pass both checks? | 15 in Hg | Go to Diagnostic Aids | ||
13 | Clean the sensor air passages. 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 EVAP tank pressure sensor. Refer to Evaporative Emission Tank Pressure Control Solenoid Valve Replace . Is the action complete? | -- | -- | |
17 | Replace the fuel tank pressure 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 |
