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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.
  1. 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. Scan tool should display FUEL TANK PRESSURE of 0 in. Hg. If reading is as specified, go to step  4 . If reading is not as specified, go to step  3 .
  2. Open fuel filler cap. Turn ignition on. Using DVOM, measure voltage (backprobe) between ground and PCM 22-pin harness connector "C" terminal No. 21 (Red/Yellow wire on Esteem, or Light Green/Yellow wire on Swift). If reading is not 2.0-2.5 volts, go to next step. If reading is 2.0-2.5 volts, go to step  4 .
  3. Check Fuel Tank Pressure Sensor (FTPS). See Figure . Go to FUEL TANK PRESSURE SENSOR under FUEL EVAPORATION in SYSTEM & COMPONENT TESTING article. Replace FTPS if it does not operate as specified. If FTPS operates as specified, check for shorts or opens between PCM harness connector "C" terminals No. 21 and 22 to FTPS, and between PCM harness connector "B" terminal No. 1 to FTPS. If wiring and connectors are okay, replace PCM.
  4. Check FTPS. Go to FUEL TANK PRESSURE SENSOR under FUEL EVAPORATION in SYSTEM & COMPONENT TESTING article. Replace FTPS if it does not operate as specified. If FTPS operates as specified, go to next step.
  5. Check Tank Pressure Control Valve (TPCV). Go to FUEL TANK PRESSURE CONTROL VALVE under FUEL EVAPORATION in SYSTEM & COMPONENT TESTING article. Replace TPCV if it does not operate as specified. If TPCV operates as specified, go to next step.
  6. Check EVAP Canister Air Valve (ECAV). Go to EVAP CANISTER AIR VALVE CIRCUIT under FUEL EVAPORATION in SYSTEM & COMPONENT TESTING article. 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.
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