DTC P0451: Evaporative (EVAP) Emission Control System Pressure Sensor Performance

NOTE: If other DTCs are set with DTC P0450, check PCM Light Green wire (sensor reference voltage) or Light Green/Black wire (sensor ground) for open circuit.

Check fuel tank pressure sensor operation. See SYSTEM/COMPONENT TESTS article. If operation is as specified, go to next step. If operation is not as specified, repair as necessary. Retest system.
Remove fuel filler cap. Turn ignition on. Using a voltmeter, measure voltage (backprobe) between ground and PCM harness connector "C", terminal No. 21. If reading is about 2.0-2.5 volts, go to next step. If reading is not as specified, check Light Green wire, Light Green/Yellow wire and Light Green/Black wire for an open or short. Repair as necessary. If wires are okay, replace PCM. Retest system.
Check fuel tank pressure control valve operation. See SYSTEM/COMPONENT TESTS article. If operation is as specified, check for an intermittent problem. See TESTS W/O CODES article. If operation is not as specified, repair as necessary. Retest system. If DTC P0450 is set, check canister air valve for proper operation. Follow testing procedures in DTC P0440 , starting at step 3).