P0451
P0451General 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 ECM monitors pressure in the fuel tank by means of Fuel Tank Pressure Sensor (FTPS) during purge control valve opening or closing phase. This monitoring will determine if pressure sensor signal is stuck. The ECM sets DTC P0451 if pressure variation is smaller than the predetermined threshold. If same error code is set in the next driving cycle, the ECM illuminates the MIL.
DTC Detecting Condition:
Specification:
Schematic Diagram:
Monitor DTC Status
CAUTION: If DTCs (or pending codes) relating to FTPS are present, do ALL REPAIRS associated with those codes before proceeding with this troubleshooting tree.
1. Start engine to normal operating temperature
CAUTION: Evaporative Emissions Systems (EVAP) Leak Tests can be run by the Scan Tool. The tests are automated and provide either a pass-fail result or directions to check for DTCs.
2. Install scan tool and clear DTC
3. Perform "EVAP. LEAKAGE TEST" mode referring to enable conditions as below
CAUTION: EVAP. Leakage Test enable conditions
- Following conditions must be fulfilled to start the test.
1. Engine warm up at Idle Status
2. No relevant DTC
3. Fuel level is below 80%
4. Is DTC P0451 set again?
YES
a. Go to next step as below
NO
a. Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM memory was not cleared. 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
Terminal and Connector Inspection
1. Many malfunctions in the electrical system are caused by poor harness(es) 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
a. Repair as necessary and go to "Verification of Vehicle Repair" procedure
NO
a. Go to "Fuel Tank Pressure Sensor (FTPS) inspection" procedure
Component Inspection
1. Ignition "ON" & Engine "OFF".
2. Measure voltage between terminal 2 of the sensor harness connector and chassis ground (Do not disconnect FTPS harness connector)
Specification : Voltage increases proportionally with decreasing pressure (Approx. 2.5 V to 4.5 V)
3. Is voltage within the specification?
YES
a. Go to "Purge Control Solenoid Valve (PCSV) Inspection" procedure
NO
a. Check for cracks or damage in hose connecting canister and fuel pump. Repair or replace as necessary.
b. Check for open or short in FTPS harness. Repair as necessary. If OK, test with a new FTPS and check for proper operation. If problem is corrected, replace FTPS and go to "Verification of Vehicle Repair" procedure
Verification of Vehicle Repair
1. Reconnect all EVAP hardware that was previously disconnected
2. Start engine to normal operating temperature
CAUTION: Evaporative Emissions Systems (EVAP) Leak Tests can be run by the Scan Tool. The tests are automated and provide either a pass-fail result or directions to check for DTCs.
3. Install scan tool and clear DTC
4. Perform "EVAP. LEAKAGE TEST" mode referring to enable conditions as below
CAUTION: EVAP. Leakage Test enable conditions
- Following conditions must be fulfilled to start the test.
1. Engine warm up at Idle Status
2. No relevant DTC
3. Fuel level is below 80%
5. Monitoring for (pending) DTC.Is the same DTC set?
YES
a. Go to the applicable troubleshooting procedure.
NO
a. System performing to specification at this time.