P0451

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

If the amplitude of fuel tank pressure signal is out of the threshold value, the PCM determines that a fault exists and a DTC is stored.





DTC Detecting Condition





Schematic Diagram

TERMINAL&CONNECTOR INSPECTION

1. Many malfunctions in the electrical system are caused by poor harness and terminals.
Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

3. Has a problem been found?

YES:

- Repair as necessary and go to "Verification of Vehicle Repair" procedure.

NO:

- Go to " Component Inspection " procedure.

Component Inspection

1. Check FTPS
(1) Engine "ON"
(2) Measure voltage between terminal "3" of FTPS connector and chassis ground.
A. Specification : 2.4 ~ 2.6 V(at idle)





(3) Is the measured voltage within specifications ?

YES

- Go to "Check PCM" as below.

NO

- 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.

2. Check PCM
(1) Ignition "OFF"
(2) Connect Scantool and Ignition "ON" & Engine "OFF"
(3) Select simulation function on scantool.
(4) Simulate voltage at terminal "3" of FTPS signal connector.
A. Specification : 2.4 ~ 2.6 V(at idle)





(5) Does the signal value of FTPS change according to simulation voltage ?

YES

- Thoroughly check connectors for looseness, poor connection, bending,corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

NO

- Substitute with a known-good PCM and check for proper operation. If the problem is corrected,replace PCM and then 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. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs.
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Monitor that all readiness test have been verified as " Complete "
5. Are any DTCs present ?

YES: Go to the applicable troubleshooting procedure.

NO: System is performing to specification at this time.