DTC P0446
Diagnostic Instructions
DTC Descriptor
DTC P0446 00: Evaporative Emission (EVAP) Vent
System Performance |
Circuit/System Description
This DTC tests the evaporative emission (EVAP) system for a
restricted or blocked EVAP vent path. The engine control module
(ECM) commands the EVAP canister purge solenoid valve open and the
EVAP canister vent solenoid valve closed. This allows vacuum to be
applied to the EVAP system. Once a calibrated vacuum level has been
reached, the ECM commands the EVAP canister purge solenoid valve
closed and the EVAP canister vent solenoid valve open. The ECM
monitors the fuel tank pressure sensor for a decrease in vacuum. If
the vacuum does not decrease to near 0 kPa (0 PSI) in a calibrated
time, this DTC sets.
Fuel Tank Pressure Sensor Signal Voltage
|
Fuel Tank Pressure
|
Low, Approximately 1.5 V or less
|
Positive Pressure
|
High, Approximately 1.5 V or more
|
Negative Pressure / Vacuum
|
|
|
Conditions for Running the DTC
• |
DTCs P0449 00, P0451 00, P0452
00, P0453 00, P0454 00, P0498 00, P0499 00, P0562 00, P0563 00,
P0642 00, P0643 00 are not set. |
• |
The ignition voltage is
between 10-18 V. |
• |
The EVAP system is
purging. |
• |
DTC P0446 00 runs once per
trip when the above conditions have been met. |
Conditions for Setting the DTC
• |
The fuel tank pressure sensor
is more than -2 kPa (-0.3 PSI) vacuum for 2 s during the 13 min
test. |
• |
The fuel tank pressure sensor
is less than -0.6 kPa (-0.1 PSI) or more than 1.2 kPa (0.2 PSI) for
3 s after a cold start ignition ON. |
• |
The fuel tank vacuum is
greater than a calibrated amount for a calibrated period of
time. |
Action Taken When the DTC Sets
DTC P0446 00 is a Type B DTC.
Conditions for Clearing the DTC
DTC P0446 00 is a Type B DTC.
Diagnostic Aids
• |
An intermittent condition may
be caused by a damaged EVAP vent housing, a temporary blockage at
the EVAP canister vent solenoid valve inlet, or a pinched vent
hose. A blockage in the vent system will also cause a poor fuel
fill condition. |
• |
An EVAP canister, vent hose,
or EVAP canister vent solenoid valve that has restricted flow may
cause this DTC to set. Using a EVAP canister purge solenoid valve
command with a scan tool will allow vacuum to be applied to the
system instead of pressure. With the engine running, the EVAP
canister vent solenoid valve open, and the EVAP canister purge
solenoid valve commanded to 100%, the fuel tank vacuum should not
increase to more than 1.2 kPa (0.2 PSI). |
• |
Disconnecting one component at
a time while the EVAP system is under flow will help to pinpoint a
restriction in the system. |
Reference Information
Connector End View Reference
Component Connector End Views
Description and Operation
Evaporative Emission Control System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
• |
EN 41413-200
Evaporative Emissions System Tester |
• |
GE 41415-50
Fuel Tank Cap Adapter |
For equivalent regional tools, refer to
Special Tools .
Circuit/System Verification
1. |
Ignition ON and fuel cap
removed, verify that the scan tool Fuel Tank Pressure Sensor
parameter is between 1.3-1.7 V. |
⇒ |
If not within the specified range, go to the B150
Fuel Tank Pressure Sensor section in Circuit/System Testing. |
|
Caution: Do
not allow the FTP sensor voltage to exceed 4.5 volts or fuel tank
damage may occur. |
3. |
With the engine running, the
Q13 Evaporative Emission Vent Solenoid Valve open and the Q12
Evaporative Emission Purge Solenoid Valve commanded to 100%, the
fuel tank vacuum should not increase to more than -2 kPa (-0.3
PSI). |
⇒ |
If the fuel tank vacuum is greater than the
specified range, go to the restriction section in Circuit/System
Testing. |
4. |
Operate the vehicle within the
conditions for running the DTC. You may also operate the vehicle
within the conditions that you observed from the freeze
frame/failure records data. |
Circuit/System Testing
• |
Perform the Circuit/System
Verification before proceeding with the Circuit/System
Testing. |
• |
Refer to the EN
41413-200 Evaporative Emissions System Tester operation
manual for detailed instructions. |
Restriction
With the engine running, the Q13 Evaporative Emission Vent Solenoid
Valve open, and the Q12 Evaporative Emission Purge Solenoid Valve
commanded to 100%, the fuel tank vacuum should not increase to more
than -2 kPa (-0.3 PSI).
If the fuel tank vacuum is greater than the specified value,
isolate the restriction by disconnecting one component at a time
while the Q12 Evaporative Emission Purge Solenoid Valve is
commanded to 100% and the vent valve is open.
Fuel Tank Pressure Sensor
1. |
Ignition ON and fuel cap
removed, verify that the scan tool Fuel Tank Pressure Sensor
parameter is between 1.3-1.7 V. |
⇒ |
If the scan tool Fuel Tank Pressure Sensor
parameter is not within the specified range, test the B150 Fuel
Tank Pressure Sensor low reference circuit for an open or high
resistance. If the circuit tests normal, replace the B150 Fuel Tank
Pressure Sensor. |
2. |
With the GE 41415-50
Fuel Tank Cap Adaptor , connect the EN 41413-200
Evaporative Emissions System Tester to the fuel filler
neck. |
4. |
Allow the engine to
idle. |
5. |
Use the purge/seal function to
seal the system with a scan tool. |
6. |
Command the Q12 Evaporative
Emission Purge Solenoid Valve to 30%. |
7. |
Observe the vacuum/pressure
gauge on the EN 41413-200 Evaporative Emissions
System Tester and the scan tool Fuel Tank Pressure Sensor
parameter. |
8. |
Allow the vacuum to increase
on the gauge of the EN 41413-200 Evaporative
Emissions System Tester until it reaches approximately 4 kPa (27.4
PSI), or until the vacuum reached the abort limit on the scan
tool. |
⇒ |
If the difference between the scan tool Fuel Tank
Pressure Sensor parameter and the vacuum/pressure gauge on the
EN 41413-200 Evaporative Emissions System Tester
more than 1 kPa (0.1 PSI), replace the B150 Fuel Tank Pressure
Sensor. |
⇒ |
If the scan tool Fuel Tank Pressure Sensor
parameter display was less than 3.2 V, replace the B150 Fuel Tank
Pressure Sensor. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
Control Module References for ECM replacement, setup and
programming
Repair Verification
Note: Larger volume fuel
tanks and or those with lower fuel levels may require several
minutes for the floating indicator to stabilize.
With the engine running, the Evaporative Emission Vent Solenoid
Valve open and the Evaporative Emission Purge Solenoid Valve
commanded to 100%, the fuel tank vacuum should not increase to more
than -2 kPa (-0.3 PSI).
|