DTC P0451

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

General Description 

Courtesy of HONDA, U.S.A., INC.

Courtesy of HONDA, U.S.A., INC.

Courtesy of HONDA, U.S.A., INC.

The fuel tank pressure (FTP) sensor is installed on the evaporative emission (EVAP) canister. The FTP sensor is used to detect leaks in the EVAP system. The powertrain control module (PCM) monitors the FTP sensor output voltage. The FTP sensor output voltage rises as the fuel tank pressure increases. Conversely, the FTP sensor output voltage drops as the fuel tank pressure decreases. Rapid changes in the FTP sensor output voltage due to electrical noise or an intermittent open during the EVAP leak detection may cause incorrect leak detection, so abnormal output is monitored. If the FTP sensor output voltage change occurs for specified ratio within a set time, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type 

Execution	Once per driving cycle
Sequence	None
Duration	31 seconds or more
DTC Type	Two drive cycles, MIL on

Enable Conditions 

Condition	Minimum	Maximum
Elapsed time after starting the engine	10 seconds	-
Engine coolant temperature [ECT SENSOR 1]	140 deg. F (60 deg. C)* 1, 131 deg. F (55 deg. C)* 2	-
12 volt battery voltage [BATTERY]	10.5 V	-
EVAP canister purge valve duty [EVAP PC DUTY]	Other than 0 %
Fuel feedback	During deceleration
Other	Other than purge-cut operation

*1: M/T model

*2: CVT model

[ ]: HDS Parameter

Malfunction Threshold 

The FTP sensor output voltage fluctuation occurs for more than 50 % within the set time at least 31 seconds.

Possible Cause 

NOTE:  The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

• FTP sensor electrical noise over lapped

Confirmation Procedure 

Operating Condition 

Courtesy of HONDA, U.S.A., INC.

• Start the engine, and let it idle until the radiator fan comes on.
• Drive the vehicle at a steady speed 35 mph (60 km/h) for at least 10 seconds.
• Decelerate with the throttle valve fully closed.
• Repeat Driving Pattern steps 2 through 3, three times.

• Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

With the HDS 

None.

Diagnosis Details 

Conditions for setting the DTC 

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC 

The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.