DTC P0451: FTP 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 the FTP sensor voltage with the scan tool or the HDS, or measure voltage between PCM connector terminals A29 and C18.
   Fig 1: Measuring Voltage Between PCM Connector Terminals A29 & C18

   Courtesy of AMERICAN HONDA MOTOR CO., INC.

   Is there about 2.5 V? 

   1. YES  -Go to step 4.
   2. NO  -Replace the FTP sensor.
4. Turn the ignition switch OFF.
5. Remove the EVAP canister cover (see step 1 on EVAP Canister Replacement  ).
6. Disconnect the hose between the EVAP two way valve and the FTP sensor at the EVAP two way valve end.
7. Connect a vacuum pump to the open end of that hose.
   Fig 2: Connecting Vacuum Pump

   Courtesy of AMERICAN HONDA MOTOR CO., INC.
8. Turn the ignition switch ON (II).
NOTE: Do not apply too much vacuum or you will damage the FTP sensor.
Fig 3: Measuring Voltage Between PCM Connector Terminals A29 & C18
Courtesy of AMERICAN HONDA MOTOR CO., INC.
9. Monitor the FTP sensor voltage with the scan tool or the HDS, or measure voltage between PCM connector terminals A29 and C18, and slowly squeeze the vacuum pump a little while watching the voltage.
10. The voltage should smoothly drop from about 2.5 V to about 1.5 V. Stop applying vacuum when the voltage drops to about 1.5 V or damage to the FTP sensor may occur.

    Does the voltage drop to about 1.5 V and hold? 

    1. YES  -Substitute a known-good PCM and recheck (see HOW TO SUBSTITUTE THE PCM FOR TESTING ). If the symptom/indication goes away, replace the original PCM.
    2. NO  -Replace the FTP sensor.