P0451
DTC P0451 EVAP. EMISSION SYSTEM-PRESSURE SENSOR RANGE / PERFORMANCEComponent Location:
GENERAL DESCRIPTION
The Fuel Tank Pressure Sensor(FTPS) converts fuel tank pressure to a proportional analog voltage signal which is read by the engine controller for evaluation during execution of the Evaporative System Diagnostic. The Tank Pressure may be below atmospheric pressure (i.e.. a vacuum) or above atmospheric pressure.
The fuel tank pressure is used to measure the difference between the air pressure (or vacuum) in the fuel tank and the ambient air pressure. The Powertrain Control Module (ECM) supplies a 5-volt reference and a ground to the sensor, which allows the sensor's output voltage to range from 0.1 to 4.9 volts. When the air pressure in the fuel tank is equal to the ambient air pressure, as when the fuel cap is removed, the output voltage of the sensor will be from 1.3 to 1.7 volts.
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 Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC Detecting Condition:
Specification:
Schematic Diagram:
MONITOR SCANTOOL DATA
1. IG "OFF" & connect Scantool.
2. ENG "ON" and warm -up the engine to normal operating temperature.
3. Monitor "FTPS" parameter on the service data.
4. Is the "FTPS" data displayed correctly?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
NO: Go to "Terminal and Connector Inspection" 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.5 V
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 resistance 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.0 V
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 Scantool to DLC(Data Link Connector).
Specification:
2. Monitor "FTPS" parameter with acceleration on service data.
3. Does the "FTPS" parameter with acceleration 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. 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 tests have been verified as "Complete"
5. Are any DTCs present?
YES: Go to the applicable trouble shooting procedure.
NO: System is performing to specification at this time.