Fuel Tank Pressure Sensor Diagnosis

Diagnosis

^ The EVAP system can be diagnosed by using EVAP Control System Diagnosis.
^ EVAP canister purge valve operation is covered in this section and diagnosed in DTCs P0440, P0446, and P1441.
^ EVAP vent solenoid operation is covered in this section and diagnosed in DTCs P0440, P0442, and P0446.
^ Fuel tank vapor pressure sensor operation is covered in this section and diagnosed in DTCs P0440, P0442, P0446, P1441 and Evaporative Emission System Check.
^ A open or shorted circuit in the EVAP canister purge valve and EVAP vent solenoid can also be diagnosed in PCM Outputs Diagnosis.

Visual Check of the EVAP Canister.

If cracked or damaged, replace canister.

Circuit Description

The fuel tank pressure sensor is used to detect vacuum decay and excess vacuum during the EVAP diagnostic routine. The sensor responds to changes in fuel tank pressure or vacuum. The signal voltage to the PCM vanes from a minimum of about 0.2 volts with pressure in the fuel tank to above 4 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 barometric pressure. Because of this, Fuel Tank Pressure may not accurately reflect the actual Output of the sensor or conditions within the fuel tank.

The Fuel Tank Pressure Sensor Diagnosis is intended to isolate and diagnose electrical problems with the sensor wiring or the sensor.

Diagnostic Aids

Check for the following conditions:

^ Inspect the PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and for poor terminal to wire connections.
^ Inspect the wiring harness for damage. If the harness appears to be OK, observe the Fuel Tank Pressure display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.

Test Description

1. The Powertrain OBD System Check prompts the technician to use the Capture Info. selection on the scan tool. This creates an electronic copy of the freeze frame data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. Refer to the Engine Fuel for the fuel tank removal procedure.
5. A normal fuel tank pressure sensor voltage output with no pressure or vacuum on the fuel system should be between 1.3 V and 1.7 V.
14. Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be be performed. Refer to the latest Techline information for PCM programming and the Powertrain Control Module for the Crankshaft Position System Variation Procedure. Testing and Inspection