P0451
DTC P0450 or P0451
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0450
- Fuel Tank Pressure (FTP) Sensor Circuit
DTC P0451
- Fuel Tank Pressure (FTP) Sensor Performance
Typical Scan Tool Data
Circuit/System Description
The control module monitors the fuel tank pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the evaporative emission (EVAP) diagnostic test. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. This DTC sets if the engine control module (ECM) detects one of the following conditions:
* The FTP sensor signal voltage is not within a calibrated range on a cold start-up.
* The FTP sensor signal oscillates greater than a calibrated amount when vehicle speed is within a predetermined range.
The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.
Conditions for Running the DTC
P0450
* DTC P0100, P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0443, P0449, P0458, P0459, P0498, P0499, P0506, P0507, P050A, P0700, P2227, P2228, or P2229 is not set.
* The engine is operating.
* The ambient air temperature is greater than -7°C (+19°F).
* The vehicle speed is less than 30 km/h (19 mph).
* The ECM has commanded the EVAP canister vent valve open for greater than 4 seconds.
* DTC P0450 runs continuously once the above conditions are met for approximately 25 seconds.
P0451 Condition 1
* DTC P0100, P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0443, P0449, P0458, P0459, P0498, P0499, P050A, P0506, P0507, P0700, P2227, P2228, or P2229 is not set.
* The engine is operating for greater than 1 seconds.
* The engine is idling.
* The ambient air temperature is warmer than -7°C (+19°F).
* The vehicle speed is less than 10 km/h (6 mph) for greater than 30 seconds.
* The BARO is greater than 68 kPa.
* The fuel level is between 11-88 percent.
* The ECM has commanded the EVAP canister purge solenoid ON.
* The ECM has commanded the EVAP canister vent valve closed for greater than 4 seconds.
* DTC P0451 runs continuously once the above conditions are met for approximately 25 seconds.
P0451 Condition 2
* DTC P0100, P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0443, P0449, P0458, P0459, P0498, P0499, P050A, P0506, P0507, P0700, P2227, P2228, or P2229 is not set.
* The engine is operating.
* The BARO is greater than 68 kPa.
* The ECM has commanded the EVAP canister purge solenoid OFF.
* The ECM has commanded the EVAP canister vent valve open.
OR
* The vehicle speed is between 10-76 km/h (6-47 mph) for greater than 30 seconds.
* The fuel level is between 11-73 percent.
* The EVAP purge solenoid is commanded ON.
OR
* The calculated ambient air temperature is 4-35°C (39-95°F) for greater than 3 seconds.
* DTC P0451 runs continuously once the above conditions are met for approximately 7 seconds.
Conditions for Setting the DTC
P0450
The ECM detects that the FTP sensor signal oscillates greater than 6.09 mm/Hg (3.26 in. H2O) for 4 seconds, or for a cumulative of 30 seconds.
P0451
* The ECM detects that the FTP is less than -26.2 mm/Hg (-14.1 in. H2O) or greater than 11.0 mm/Hg (5.9 in. H2O) for 4 seconds or for a cumulative of 30 seconds.
OR
* The ECM detects a change in the zero point of FTP sensor signal greater than +/-5.16 mm/Hg (2.76 in. H2O) from the zero point at start up for 4 seconds, or a cumulative of 30 seconds.
Action Taken When the DTC Sets
* DTC P0450 is Type B DTC.
* DTC P0451 is Type B DTC.
Conditions for Clearing the MIL/DTC
* DTC P0450 is Type B DTC.
* DTC P0451 is Type B DTC.
Diagnostic Aids
* A blocked or clogged EVAP canister vent solenoid valve, or inlet tube may set these DTCs.
* A stuck open EVAP purge solenoid valve may set these DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Fuel System Description (Fuel System Description)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning)for scan tool information
Special Tools
* J 41413-SPT High Intensity White Light
* J 41413-VLV EVAP Port Vent Fitting Tool
* J 41413-200 Evaporative Emissions System Tester (EEST)
* J 41413-300 EVAP Cap and Plug Kit
* CH-48096 EVAP Service Port Access Tool
* GE-41415-50 Fuel Tank Cap Adapter
Circuit/System Testing
1. Ignition OFF, disconnect the EVAP purge solenoid valve harness connector.
2. Engine idling, command the EVAP vent solenoid valve CLOSED with a scan tool.
3. Increase the engine speed to 1,200-1,500 RPM. Verify the scan tool fuel tank pressure (FTP) sensor parameter is within -0.9 to +0.9 mmHg (-0.5 to +0.5 in.H2O).
• If not within the specified range, replace the EVAP purge solenoid valve.
4. Ignition OFF, remove the fuel fill cap. Connect the GE-41415-50 to the fuel tank filler neck. Connect the J 41413-200 to the GE-41415-50 .
5. Ignition ON, command the EVAP vent solenoid valve CLOSED with a scan tool.
6. Pressurize the EVAP system with nitrogen to 9.33 mm/Hg (5 in/H2O). Compare the scan tool Fuel Tank Pressure Sensor parameter to the J 41413-200 pressure/vacuum gauge. Verify the FTP sensor parameter is within +/-0.9 mmHg (+/-0.5 in.H2O) of the pressure/vacuum gauge.
• If not within the specified range, replace the FTP sensor.
7. Command the EVAP vent solenoid valve OPEN with a scan tool. Verify the scan tool FTP sensor parameter is within +/-0.9 mmHg (+/-0.5 in.H2O).
• If not within the specified range, test or replace the EVAP canister vent solenoid valve and vent pipe for a blockage or restriction.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Fuel Tank Pressure Sensor Replacement (Fuel Tank Pressure Sensor Replacement)
* Evaporative Emission Canister Purge Solenoid Valve Replacement (Service and Repair)
* Evaporative Emission Canister Vent Solenoid Valve Replacement (Service and Repair)