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

WARNING: This work must be performed in a well ventilated area away from any open flame.

If not using scan tool, go to next step. If using scan tool, turn ignition off and connect scan tool to Data Link Connector (DLC). Open fuel filler cap. Turn ignition on. Fuel tank pressure display should read 0 in. Hg. If reading is as specified, go to step 4). If reading is not as specified, go to step 3).
Open fuel filler cap. Turn ignition on. Measure voltage (backprobe) between ground and PCM harness connector "C" terminal No. 21 (Red/Yellow wire). If voltage is not 2.0-2.5 volts, go to next step. If voltage reads 2.0-2.5 volts, go to step 4).
Check Fuel Tank Pressure Sensor (FTPS). See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS article. Replace FTPS if it does not operate as specified. If FTPS operates as specified, check Pink/Green wire, Red/Yellow wire, and Blue wire for any shorts or opens. If wiring and connectors are okay, replace PCM.
Check FTPS. See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS article. Replace FTPS if it does not operate as specified. If FTPS operates as specified, go to next step.
Check Tank Pressure Control Valve (TPCV). See DTC P0440 : EVAPORATIVE (EVAP) EMISSION CONTROL SYSTEM MALFUNCTION OR DTC P0455: EVAPORATIVE (EVAP) EMISSION CONTROL SYSTEM GROSS LEAK, steps 5) and 6). Replace TPCV if it does not operate as specified. If TPCV operates as specified, go to next step.
Check EVAP Canister Air Valve (ECAV). See DTC P0440 : EVAPORATIVE (EVAP) EMISSION CONTROL SYSTEM MALFUNCTION OR DTC P0455: EVAPORATIVE (EVAP) EMISSION CONTROL SYSTEM GROSS LEAK, steps 10), 11) and 12). Replace ECAV if it does not operate as specified. If ECAV operates as specified, problem is intermittent or due to a faulty PCM. Repair as necessary and retest system.