Fuel System > Engine Control System > P0451 Evaporative Emission System-Pressure Sensor Range / Performance

Component Location

General Description

The evaporative emission control system prevents hydrocarbon vapors from escaping from the fuel tank into the atmosphere where they could form photochemical smog. Gasoline vapors are collected in the charcoal canister. The Fuel Tank Pressure Sensor (FTPS) is an integral part of the evaporative monitoring system. The PCM monitors the FTPS signal to detect vacuum decay and excess vacuum. The FTPS measures the difference between the air pressure inside the fuel tank and outside air pressure to check the purge control solenoid valve operation and for leak detection in the evaporative emission control system by monitoring pressure and vacuum levels in the fuel tank during the purge control solenoid valve operating cycles.

DTC Description

Checking output signals of tank pressure under detecting condition, if the tank pressure does not change less than 0.2(0.05V) within 3min. , PCM sets P0451. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

DTC Detecting Condition

Item

Detecting Condition

Possible cause

DTC Strategy

•	Continuously monitors the fuel tank pressure sensor output for a stuck condition

•	Hose between Canister and Tank is not connected.

•	Faulty FTPS

Enable Conditions

Case 1

•	Engine Coolant Temperature ≥ 60°C (Fully Warmed up state)

•	600rpm < Engine Speed < 3000rpm

Case 2

•	During the EVAP. Monitoring

Threshold value

Case 1

•	Pressure change in tank < 0.2 (0.05V)

Case 2

Before large leak monitoring has completed

•	Pressure sensor is detected as stuck

•	Pressure change in tank < 0.2 (0.05V)

Diagnosis Time

•	Continuous (Within 3min : Before EVAP. Monitoring has completed )

MIL On Condition

•	2 Driving Cycles

Specification

Pressure(kPa)	Output Voltage(V)
-3.75	4.5
0	1.5
1.25	0.5

Schematic Diagram

Monitor DTC Status

Check DTC Status

(1)	Connect scantool to Data Link Connector(DLC).

(2)

IG "ON".

(3)	Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.

(4)	Read "DTC Status" parameter.

(5)

Is parameter displayed "Present fault"?

	▶ Check that hose between canister and tank is correctly connected or missing. Repair or replace as necessary and then, go to "Component Inspection" procedure.
	▶ Fault is intermittent caused by PCM memory was not cleared after repair. Erase DTC and go to " Verification of Vehicle Repair" procedure.

Component Inspection

1.	IG "OFF" & connect scantool.

ENG "ON" and Race the accelerator pedal at idle and Monitor "FTPS" parameter is changing while PCSV is operating on the service data.

Specification : Fuel Tank Pressure is O.K if pressure changes more than 0.2 while racing accelerator padal.

Does the FTPS change while racing the accelerator pedal at idle ?

	▶ Fault is intermittent. Drive the vehicle to satisfy the enable codition then, go to "Verification of Vehicle Repair " procedure.
	▶ Substitute with a known - good FTPS and check for proper operation. If the problem is corrected, replace FTPS and go to "Verification of Vehicle Repair" procedure.

Verification Of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.

1.	Connect scantool and select "DTC" button.

2.	Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions

3.	Read "DTC Status" parameter

Is parameter displayed "History(Not Present) fault"?

	▶ System performing to specification at this time. Clear the DTC
	▶ Go to the applicable troubleshooting procedure.