Circuit Description
The fuel tank pressure sensor is used in order to detect a vacuum decay or an excessive vacuum during the EVAP diagnostic routine. The fuel tank pressure sensor responds to the changes in the fuel tank pressure or vacuum. The signal voltage to the Powertrain Control Module (PCM) varies from a minimum of about 0.2 volts with pressure in the fuel tank to above 4.0 volts with a high vacuum in the fuel tank.
The fuel tank pressure display on the scan tool has an auto zero feature which occurs at each ignition cycle and is corrected according to the barometric pressure. Because of this, the fuel tank pressure may not accurately reflect the actual output of the sensor or the conditions within the fuel tank.
Conditions for Setting the DTC
The fuel tank pressure sensor voltage is more than 4.9 volts for more than 25 seconds.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information. |
| • | A history DTC stores. |
Conditions for Clearing the MIL/DTC
| • | The malfunction indicator lamp (MIL) will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
Check for the following conditions:
| • | Inspect the Control Module harness connectors for the following conditions: |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed |
| - | Damaged terminals |
| • | Inspect the wiring harness for damage. If the harness appears to be OK, observe the Fuel Tank Vacuum display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the display will indicate the location of the fault. |
Refer to (Link no longer avaliable) before starting repairs.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.
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This step will determine if DTC P0453 is the result of a hard malfunction or an intermittent condition.
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This step simulates conditions for a DTC P0452. If the PCM recognizes the change, that indicates the PCM, the Fuel Tank Pressure sensor 5.0 V reference circuit and the Fuel Tank Pressure sensor signal circuit are OK.
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This step looks for an open in the Fuel Tank Pressure sensor ground circuit.
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When the Fuel Tank Pressure sensor signal circuit is shorted to battery voltage, the TP will be displayed above 0% at all times and the A/C High Side will be displayed high. The vehicle will also remain in Open Loop.
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Important: The Powertrain Control Module (PCM) uses a single 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.
Disconnect all the sensors that use a 5.0 volt reference one at a time while monitoring the short on the 5.0 volt reference circuit. Check and repair any circuit or replace any sensor that may have caused the short on the 5.0 volt reference circuit.
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Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline information for PCM programming and for the Crankshaft Position System Variation Procedure.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to | ||
Does the scan tool display a Fuel Tank Pressure value of the specified value or more? | 3.0 V | |||
Does the scan tool display a Fuel Tank Pressure value of the specified value or less? | 0.2 V | |||
4 |
Does the scan tool display a Fuel Tank Pressure value equal to or greater than the specified value? | 3.0 V | Go to Diagnostic Aids | |
Connect a test light to battery voltage and probe the Fuel Tank Pressure sensor ground circuit terminal. Does the test light illuminate? | -- | |||
Was a repair necessary? | -- | |||
7 | Connect a DMM to ground and probe the Fuel Tank Pressure sensor 5.0 volt reference circuit. Does the DMM display near the specified value or less? | 5.0V | ||
|
Important: The Powertrain Control Module (PCM) uses a single 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.
Was a repair necessary? | -- | |||
9 | Check for an open or a poor electrical connection in the Fuel Tank Pressure sensor ground circuit and repair the connection as necessary Was a repair necessary? | -- | ||
Check the PCM electrical connector terminals for being clean and tight, if OK replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | ||
11 | Check the Fuel Tank Pressure sensor electrical connector terminals for being clean and tight, if OK replace the Fuel Tank Pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the action complete? | -- | -- | |
12 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
13 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC table | System OK |
