P0451

DTC P0451: Fuel Sensor 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 FTP sensor voltage with the Honda PGM Tester, or measure voltage between ECM connector terminals A29 and C18.

Is there about 2.5 V?

YES - Go to step 4.

NO - Replace the FTP sensor.

4. Turn the ignition switch OFF.




5. Disconnect the hose between the EVAP two-way valve and the fuel tank pressure sensor (A) at the EVAP two-way valve end.
6. Connect a vacuum pump to the open end of that hose.
7. Turn the ignition switch ON (II).




8. Monitor the FTP sensor voltage with the Honda PGM Tester, or measure voltage between ECM connector terminals A29 and C18, and carefully squeeze the vacuum pump a little.
9. The voltage should smoothly drop from about 2.5 V down to about 1.5 V. Stop applying vacuum when the voltage drops to about 1.5 V or damage to the fuel tank pressure sensor may occur.

Does the voltage drop to about 1.5 V and hold?

YES - Check for misrouted, leaking, or broken FTP sensor vacuum lines. If the vacuum lines are OK. Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.

NO - Replace the FTP sensor.