Circuit Description
The DTC P0452 Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage diagnostic monitors the function of the FTP sensor circuit. Emission laws require that the powertrain control module (PCM) detect any leakage within the EVAP system. The PCM tests the EVAP system for leaks by monitoring the vapor pressures in the fuel tank with the FTP sensor. The FTP sensor contains a silicon based chip that changes electrical resistance when pressure is applied. The PCM supplies a 5-volt reference, an electrical ground, and a signal return circuit that has a 5-volt bias. The FTP sensor signal voltage varies from a minimum of about 0.2 volts with negative pressure in the fuel tank, to a maximum of more than 4 volts with positive pressure in the fuel tank.
Fuel Tank Vapor Space | FTP mm Hg | FTP Signal Voltage |
|---|---|---|
Pressure | Positive Value | High |
No Pressure | Near Zero | 2.5-2.6 V |
Vacuum | Negative Value | Low |
Conditions for Running the DTC
| • | The engine coolant temperature is -8 to +110°C (18-230°F). |
| • | The intake air temperature is -14 to +70°C (7-158°F). |
| • | The engine has been running at idle for at least 2 minutes. |
Conditions for Setting the DTC
The fuel tank pressure is lower than -49.5 mm Hg (-26.5 in H2O).
OR
Fuel tank pressure sensor signal voltage is less than 0.5 volts.
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 in order to clear the DTC. |
Diagnostic Aids
Check for any of the following conditions:
| • | A plugged sensor air vent hole. Inspect the sensor and clean if necessary. |
| • | If a DTC P0452 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Evaporative Emission System Set . |
An intermittent malfunction may be caused by a fault in the fuel tank pressure sensor electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .
If a DTC P0452 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the 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 Diagnostic System Check-Engine Controls 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.
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This step determines if a fault is present. The fuel tank pressure sensor reading indicated on the scan tool will vary with the surrounding barometric pressure.
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Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio.
The 5 volt reference circuit is shared internally in the PCM with the FTP sensor. Be sure to inspect the FTP sensor reference circuit for a short to ground.
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The 5 volt reference circuit is shared internally in the PCM with other engine control sensors. Be sure to inspect all shared reference circuits for a short to ground.
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Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0452 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0452 appears in the Not Ran Since Code Cleared list, the P0452 diagnostic has not yet run. When DTC P0452 does not appear in the Not Ran Since Code Cleared list, the P0452 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the P0452 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||
2 | Is a DTC P0103, DTC P0328 and DTC P1450 also set? | -- | Go to Step 9 | Go to Step 3 |
Is the pressure within the specified range? | 0.0-0.9 mm Hg (0.0-0.5 in H2O) | Go to Step 5 | Go to Step 4 | |
4 |
Is the voltage within the specified range? | 2.5-2.6 V | Go to Step 11 | Go to Step 6 |
Is a DTC P0452 present? | -- | Go to Diagnostic Aids | Go to Step 6 | |
6 |
Is the voltage at the specified value? | 5 V | Go to Step 7 | Go to Step 10 |
7 |
Is the fuel tank pressure indicated on the scan tool near the specified value? | 62.11 mm Hg (32.10 in H2O) | Go to Step 13 | Go to Step 8 |
8 |
Did you find and correct a condition? | -- | Go to Step 14 | Go to Step 11 |
Did you find and correct a condition? | -- | Go to Step 14 | Go to Step 12 | |
10 |
Did you find and correct a condition? | -- | Go to Step 14 | Go to Step 11 |
11 |
Did you find and correct a condition? | -- | Go to Step 14 | Go to Step 12 |
12 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
Does the DTC run and pass? | -- | Go to Step 15 | Go to Step 2 | |
15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
