Circuit/System Testing

Restriction

1. With the engine running, the EVAP canister vent solenoid valve open, and the EVAP canister purge solenoid valve commanded to 100 percent, the fuel tank vacuum should not increase to more than -15 mmHg (-8 inches H2O).
   • If the fuel tank vacuum is greater than the specified value, isolate the restriction by disconnecting one component at a time while the EVAP canister purge solenoid valve is commanded to 100 percent and the vent valve is open.
2. Using the scan tool, decrease the canister purge duty cycle from 100 percent to 0 percent. The vacuum should decrease to near zero.
   • If the fuel tank vacuum does not return to zero, or appears to decrease too slowly, inspect the components in the EVAP vent system for a restriction.

Fuel Tank Pressure Sensor

1. Ignition OFF, disconnect the harness connector at the B150 fuel tank pressure sensor.
2. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes, test for less than 5 ohms between the low reference circuit terminal and ground.
   • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the fuel tank pressure sensor.