Fuel Tank Pressure Sensor Diagnosis

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The fuel tank vapor pressure sensor is used to detect vacuum decay and excess vacuum during the Evaporative Emissions (EVAP) System diagnostic routine. The sensor responds to changes in fuel tank pressure or vacuum. The signal voltage to the PCM varies 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 Vacuum 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 Vacuum Pressure may not accurately reflect the actual output of the sensor or conditions within the fuel tank.

Table C-3C 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 Vacuum 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 fuel tank removal.

5. A normal fuel tank vapor 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 PCM's must be reprogrammed. Refer to the latest Techline information for programming procedures.