P0452

DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage




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 Running the DTC
The engine is running.

Conditions for Setting the DTC
The fuel tank pressure sensor voltage is lower than 0.1 volt 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 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.
- A scan tool can 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 EVAP System Cleaning before starting repairs.

Steps 1 - 2:

Steps 3 - 5:

Step 6:

Steps 7 - 8:

Steps 9 - 12:

Steps 13 - 14:

Test Description
1. 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.
7. A normal Fuel Tank Pressure sensor voltage output with no pressure or vacuum on the fuel system should be between 1.3 volts and 1.7 volts.
12. Replacement PCMs must be programmed and the crankshaft position system variation procedure must be performed. Refer to the latest Isuzu Technical Communications System (ITCS) information for PCM programming.