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DTC P0451: Fuel Tank Pressure Sensor Malfunction: Testing

NOTE: Ensure freeze frame data has been recorded. Check for service bulletins and on-line information.
  1. Turn ignition off. Turn ignition on. Using scan tool, check for DTCs. If DTC P0443 and/or P1449 are present, go to appropriate test. If DTCs listed are not present, go to next step.
  2. Disconnect vacuum hoses at purge solenoid valve. Apply vacuum at lower purge solenoid valve fitting. Turn ignition on. Using scan tool, activate PRGV PID to 50 percent. If vacuum is released when PRGV is activated, go to next step. If vacuum is not released, replace solenoid valve and go to step  6 .
  3. Disconnect CDCV vacuum hoses. Apply vacuum at CDCV. Using scan tool, activate CDCV PID. If vacuum is held during 3 second test when CDCV is activated, go to next step. If vacuum is not released, replace CDCV and go to step  6 .
  4. Remove charcoal canister beside fuel tank. Inspect for leaks, damage or clogging. If charcoal canister is okay, go to next step. If problem is present, replace as needed. Go to step  6 .
  5. Inspect fuel tank pressure sensor. See SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE & 626 article. Replace as needed. If fuel tank pressure sensor is okay, go to next step. If sensor is faulty, replace sensor and go to next step.
  6. Turn ignition on. Using scan tool, access PID/DATA MONITOR. Check PID data for BARO, ECT, IAT and FTL PIDs. Compare readings with specifications. See DTC P0451 TEST SPECIFICATIONS  . If all readings are within specifications, go to next step. If any readings are not within specifications, take action necessary (e.g. cool down engine). Repeat this step.
  7. Reconnect all components. Conduct Drive Mode No. 4 under DRIVE CYCLE PROCEDURE. See SELF-DIAGNOSTICS - INTRODUCTION - MIATA, MILLENIA, MPV & PROTEGE article. Stop vehicle. Using scan tool, check Drive Mode status. If evap purge system has been monitored, go to next step. If evap purge system has not been monitored, go to step  6 .
  8. Turn ignition on. Using scan tool, check FTP V PID. FTP PID should be .2-4.8 volts. Check DTCs. If DTC P0451 is pending, replace PCM and go to next step. PCM is mounted to passenger floor, behind glove box. If DTC P0451 is not pending, go to next step.
  9. Perform after repair procedure. See AFTER REPAIR PROCEDURE  . If no DTC is present, testing is complete. If any DTC is present, go to appropriate test for diagnosis and repair.
DTC P0451 TEST SPECIFICATIONS

Component Scan Tool Reading
BARO 21.3 inHg Or More
ECT 14-90.5°F
IAT 14-131°F
FTL 1.25-3.75 Volts
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