Circuit Description

Vapor pressure sensor and vapor pressure sensor Vacuum Switching Valve (VSV) are used to detect faults in EVAP system.

DTC P0450 is set if 10 seconds after engine starts, vapor pressure sensor reading is less than -1.0 in. Hg, or .4 in. Hg or more for 7 seconds or more. DTC P0450 is also set if 10 seconds after engine starts, vapor pressure sensor reading is less than -1.2 in. Hg, or .6 in. Hg or more for 7 seconds or more. DTC P0451 is set if vapor pressure sensor output changes wile vehicle is standing at idle and vapor pressure sensor VSV is on. Possible causes are:

Short or open in vapor pressure sensor circuit.
Vapor pressure sensor.
ECM.

NOTE: If DTCs P0110, P0115, P0120, P0450 and P1120 are output together, inspect ECM ground circuit for an open. Repair as necessary. See appropriate wiring diagram in SYSTEM WIRING DIAGRAMS article.