DTC P0446 Evaporative Emission (EVAP)
Vent System Performance
The PCM monitors the
performance of the EVAP system by applying a predetermined level of vacuum to
the EVAP system then monitors the vacuum decay rate. The PCM sets this DTC if
the vacuum decay rate is greater than a predetermined value.
Conditions for Running the DTC
- DTCs P0107, P0108, P0112, P0113,
P0117, P0118, P0121, P0122, P0123, P0125, P0420, P0430, P0452, P0453,
P0500, P0502, P0503, P1111, P1112, P1114, P1115 or HO2
- The ignition voltage is between 10
and 17 volts.
- The barometric pressure is more than
75 kPa.
- The fuel level is between 15% and
85% of full capacity.
- The engine coolant temperature is
between 4°C (39°F) and 30°C (86°F).
- The intake air temperature is
between 4°C (39°F) and 30°C (86°F).
- The start up engine coolant
temperature and the intake air temperature are within 9°C (16°F) of each
other.
Conditions for Setting the DTC
- The EVAP vacuum decay rate is
greater than a predetermined value.
- The conditions are present for
greater than 2 seconds.
OR
- The vacuum present in the EVAP
system is greater than a predetermined value.
- The conditions are present for
greater than 4 seconds.
Important
This DTC does not report a
first failed test. A first fail of this DTC will have a scan tool status as Not
Run.
Action
Taken When the DTC Sets
- The PCM will illuminate the
Malfunction Indicator Lamp (MIL) after two consecutive drive trips that
the diagnostic runs and fails.
- The PCM will record operating
conditions at the time the DTC sets. This information will be stored in
the Freeze Frame and Failure Records.
- A first failure of this DTC will NOT
store in Last Test Failed or History.
Conditions
for Clearing the MIL/DTC
- The PCM turns OFF the malfunction
indicator lamp (MIL) after 3 consecutive ignition cycles that the
diagnostic runs and does not fail.
- A last test failed, or current DTC,
clears when the diagnostic runs and does not fail.
- A history DTC clears after
40 consecutive warm-up cycles, if no failures are reported by this or
any other emission related diagnostic.
- Use a scan tool in order to clear
the MIL and the DTC.
Important
An accurate indication of
fuel level is required for the PCM to properly Pass or Fail this DTC. Always
diagnose the fuel level sensor DTC's before performing this DTC's diagnostic
table. Always inspect for fuel level sensor DTC's stored as History.
Important
The Service Bay Test may have
to be performed in cold ambient air temperatures when the vehicle is running a
winter grade fuel. The scan tool displays a message when the service bay test
does not run.
Conditions for Running the
- The battery voltage is between 10.5
and 17.5 volts.
- The fuel level is between 15% and
85% of the full capacity.
- The engine temperature is between
3.5°C (38°F) and 35°C (95°F).
Perform a physical
inspection of the EVAP system. Inspect for the following conditions:
- A loose, missing, defective, or
incorrect fuel tank cap
- Incorrectly routed or defective EVAP
system vacuum and vapor lines
- A stuck closed EVAP Vent Valve
- A restricted or blocked EVAP system
hose
- A restricted or stuck closed fuel
tank rollover valves
- A malfunctioning or damaged vapor
canister
Inspect for charcoal
release from the vapor canister. Refer to the EVAP
System Cleaning procedure.
The vacuum and pressure
in the EVAP system is measured in inches of water (H2O). Most gauges measure
vacuum in inches of mercury (Hg) and pressure in pounds per square inch (psi).
The following shows how the values compare:
|
in H2O |
in Hg |
psi |
|
1in H2O |
0.07 in Hg |
0.0361 psi |
|
5 in H2O |
0.36 in Hg |
0.180 psi |
|
10 in H2O |
0.73 in Hg |
0.361 psi |
|
15 in H2O |
1.10 in Hg |
0.541 psi |
The numbers below refer
to the step numbers on the Diagnostic Table.
If the Service Bay Test can not be run,
proceed to Step 5. If a fault is not currently present the diagnostic table
steps will return you to Step 3.
An open fuel tank pressure sensor ground
circuit causes this DTC to set. If the fuel tank pressure sensor does not
respond to pressure (or vacuum), inspect the ground circuit for an open.
The Fuel Tank Pressure sensor monitors a
range from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).
In order to test the Fuel Tank Pressure
sensor for vacuum response, command the EVAP Purge Solenoid Valve to 100
percent with the engine running and quickly SEAL the system. Leaving the EVAP
Purge Solenoid Valve activated for a longer period of time allows a greater
level of vacuum to develop.
|
Step |
Action |
Value(s) |
Yes |
No |
|
Did
you perform the Powertrain On-Board Diagnostic (OBD) System Check? |
-- |
|||
|
Inspect
the EVAP system for the following conditions:
Repair
the EVAP system as necessary if you find a condition. Did you find and
correct the condition? |
-- |
|||
|
Important Ensure that The Conditions
for Running the Perform the EVAP system
Service Bay Test. Does the vehicle pass the
Service Bay Test? |
-- |
Go to Diagnostic Aids |
||
Does
the vacuum drop from the specified value when the EVAP Vent Valve is opened? |
5 in. Hg. |
|||
Does
the vacuum drop from the specified value when the vent line is unplugged? |
5 in. Hg. |
|||
Did
you find and correct the condition? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
|
Important The following steps require
the EVAP pressure/purge diagnostic station J 41413 . Always zero the EVAP
Pressure and Vacuum (in. H2O) gauges on the EVAP pressure/purge diagnostic
station before proceeding with diagnosis.
Does
the Fuel Tank Pressure sensor indicate the actual amount of vacuum in the
EVAP system? |
-- |
|||
|
Replace
the EVAP Vent Valve. Refer to EVAP
Vent Valve Replacement . Is the action complete? |
-- |
-- |
||
|
Replace
the EVAP Vapor Canister. Refer to EVAP
Canister Replacement . Is the action complete? |
-- |
-- |
||
|
Replace
the Fuel Tank Pressure sensor. Refer to Fuel
Tank Pressure Sensor Replacement . Is the action complete? |
-- |
-- |
||
Does
the scan tool indicate that this test ran and passed? |
-- |
|||
|
Select
the Capture Info option and the Review Info option using the scan tool. Does
the scan tool display any DTCs that you have not diagnosed? |
-- |
Go to the applicable
DTC |
System OK |