Range/Performance Problem

DTC P0451: Fuel Tank Pressure Sensor Circuit Range/Performance Problem

Special Tools Required
Vacuum Pump/Gauge, 0 - 30 in.Hg A973X-041-XXXXX

1. Remove the fuel fill cap.
2. Turn the ignition switch ON (II).




3. Monitor the FTP sensor voltage with the Honda PGM Tester, or measure voltage between ECM/ PCM connector terminals A29 and C18.
Is there approx. 2.5 V?
YES-Go to step 4.
NO- Replace the fuel tank pressure sensor.
4. Turn the ignition switch OFF.




5. Open the fuel vent assembly cover (A) in front of the EVAP control canister.
6. Disconnect the hose between the EVAP two way valve and the fuel tank pressure sensor at the EVAP two way valve end.




7. Connect a vacuum pump to the open end of that hose.
8. Turn the ignition switch ON (II).
9. Monitor the FTP sensor voltage with the Honda PGM Tester, or measure voltage between PCM connector terminals A29 and C18, and carefully squeeze the vacuum pump one stroke at a time.
10. The voltage should smoothly drop from approx. 2.5 V down to approx. 1.5 V. STOP applying vacuum when the voltage drops to approx. 1.5 V or damage to the fuel tank pressure sensor may occur.
Does the voltage drop to approx. 1.5 V and hold?
YES-Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original ECM/PCM.
Diagnostic Strategies

NO-Replace the fuel tank pressure sensor.