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 ECM 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
The Tank Pressure Sensor Stuck Diagnostic continuously monitors the fuel tank pressure sensor output for a stuck condition. It does this by comparing the maximum and minimum raw tank pressure voltages. If the difference between the two values exceeds a threshold, then the diagnostic is considered to have passed. The diagnostic is not allowed to fail unless (a) a significant portion of the EVPD(Evaporative Diagnostics) tank draw has occurred or (b) the tank pressure has not changed after purge transitions off from a flow level high enough to cause a change in the tank pressure.
Checking output signals of tank pressure under detecting condition, if the tank pressure difference between maximum and minimum is low than 0.9996 for 60 sec, PCM sets P0451 MIL(Malfunction Indicatin Lamp) turns on when the malfunction lasts till cosecutive 2 driving cycle.
DTC DETECTING CONDITION
SPECIFICATION
SCHEMATIC DIAGRAM
MONITOR DTC STATUS
1. Connect scantool to Data Link Connector(DLC).
2. IG "ON".
3. Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC's information from the DTCs menu
4. Read "DTC Status" parameter.
5. Is parameter displayed "Present fault"?
YES
> Go to "Inspection & Repair" procedure.
NO
> Fault is intermittent, go to "Verification of vehicle Repair" procedure.
TERMINAL AND 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 " Power Circuit Inspection " procedure.
POWER CIRCUIT INSPECTION
1. IG "OFF" and disconnect FTPS connector.
2. IG "ON" & ENG "OFF"
3. Measure voltage between terminal 1 of FTPS harness connector and chassis ground.
Specification : Approx. 5V
4. Is the measured voltage within specification ?
YES
> Go to "Ground circuit inspection" procedure.
NO
> Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
GROUND CIRCUIT INSPECTION
1. IG "OFF" and disconnect FTPS connector.
2. Measure voltage between terminal 1 of FTPS harness connector and chassis ground.
3. Measure voltage between terminal 1 and 3 of FTPS harness connector.
Specification : Voltage difference between Measurement "A" and "B" is below 200mV.
4. Is the measured voltage within specification ?
YES
> Go to "Signal Circuit Inspection" procedure.
NO
> Repair contact reistance or open in harness and then go to "Verification of Vehicle Repair" procedure.
SIGNAL CIRCUIT INSPECTION
1. Check voltage.
(1) IG "OFF" and disconnect FTPS connector.
(2) IG "ON" & ENG "OFF"
(3) Measure voltage between terminal 2 of FTPS harness connector and chassis ground.
Specification : Approx. 0V
(4) Is the measured voltage within specification ?
YES
> Go to "Component Inspection" procedure.
NO
> Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1. Check FTPS.
(1) IG "OFF" and connect scatool to DLC(Data Link Connector).
(2) Monitor "FTPS" parameter with accelleration on service data.
Specification
(3) Does the "FTPS" parameter with accelleraton on the service data change ?
YES
> Go to "Check PCM" as follows.
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) IG "OFF" disconnect FTPS connector
(2) Connect Scantool and IG "ON" & ENG "OFF"
(3) Select simulation function on scantool.
(4) Simulate voltage at terminal 2 of FTPS harness connector.
(5) Does the signal value of FTP sensor 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 go to "Verification of Vehicle Repair" procedure.
NOTE:
There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM
Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
2. Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
3. Read "DTC Status" parameter.
4. Is parameter displayed "History(Not Present) fault"?
YES
> System performing to specification at this time. Clear the DTC
NO
> Go to the applicable troubleshooting procedure.