Circuit Description
The evaporative system includes the following components:
| • | The fuel tank |
| • | The EVAP vent solenoid |
| • | Fuel tank pressure sensor |
| • | The fuel pipes and hoses |
| • | The fuel vapor lines |
| • | The fuel cap |
| • | The EVAP canister |
| • | The purge lines |
| • | The EVAP canister purge solenoid valve |
| • | The EVAP service port |
The evaporative emission (EVAP) system is checked by applying vacuum to the EVAP system and by monitoring for a vacuum decay. The Powertrain Control Module (PCM) monitors the vacuum level through the fuel tank pressure sensor signal. At an appropriate time, the EVAP canister purge solenoid valve and the EVAP vent solenoid are turned ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP canister purge solenoid valve is turned OFF, sealing the system.
A restricted or blocked EVAP canister vent path is detected by:
- Drawing a vacuum on the EVAP system
- Turning OFF the EVAP vent solenoid and the EVAP canister purge solenoid valve -- the EVAP vent solenoid should be open and the EVAP purge pulse width modulator should be at 0 percent
- Monitoring the fuel tank vacuum sensor signal.
With the EVAP vent solenoid open, any vacuum in the system should decrease quickly unless the vent path is blocked. A blockage can be caused by the following conditions:
| • | A malfunctioning EVAP vent solenoid that is stuck closed |
| • | The vent hose for the following conditions: |
| - | Plugs |
| - | Kinks |
| - | Pinches |
| • | A shorted EVAP vent solenoid driver circuit |
| • | A plugged evaporative canister |
If any of these conditions are present, DTC P0446 will set.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0452, P0453, P0502, P0503, P0601, P0602, P1621, and P1133 are not set. |
| • | The BARO is more than 75 kPa. |
| • | The intake air temperature (IAT) is between 5°C and 29°C (41°F and 84°F) at engine start-up. |
| • | The engine coolant temperature (ECT)is between 5°C and 29°C (41°F and 84°F) at engine start-up. |
| • | The intake air temperature (IAT) is not more than 1°C (2°F) more than the engine coolant temperature (ECT) at start-up. |
| • | The engine coolant temperature (ECT) is not more than 7°C (12°F) more than the intake air temperature (IAT) at start-up. |
| • | The fuel tank level is between 26 percent and 74 percent. |
| • | The TP sensor is between 7 percent and 35 percent. |
Conditions for Setting the DTC
The EVAP system is unable to release vacuum during the diagnostic test.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information. |
| • | A history DTC stores. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs a pass. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a malfunction. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
Although this DTC is considered a type A diagnostic, this DTC acts like a type B diagnostic during certain conditions. Refer to Serial Data Communications . Whenever this diagnostic reports that the system has passed, or if the battery is disconnected, the diagnostic must fail twice before setting a DTC. The initial failure does not report to the diagnostic executive or display on a scan tool. A passing system always reports to the diagnostic executive immediately.
If a DTC P0461 is set along with an EVAP System DTC, the EVAP DTC cannot be considered valid until you repair and clear DTC P0461.
Inspect for the following conditions:
| • | A faulty electrical terminal connection at the PCM. Inspect the harness electrical connectors for the following conditions: |
| - | Backed-out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed connectors |
| - | Damaged terminals |
| - | A faulty terminal to wire connection |
| • | A damaged harness. Inspect the wiring harness to the EVAP vent solenoid and the fuel tank pressure sensor for an intermittent open or shorted circuit. |
| • | Verify that the vent hose between the EVAP canister and the EVAP vent solenoid is not restricted. Inspect for the following conditions: |
| - | Kinks |
| - | Pinches |
| - | A plugged vent hose |
Refer to Evaporative Emission System Cleaning for further procedures.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
-
If a vent solenoid electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction will usually correct the condition that set DTC P0446.
-
This step tests the fuel tank pressure sensor at the ambient pressure.
-
This step verifies that the fuel tank pressure sensor accurately reacts to the EVAP system pressure changes.
-
This step tests for a blocked EVAP canister.
-
This step duplicates the Powertrain On-Board Diagnostic test.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
2 |
Is DTC P0452, P0453 or P0461 also set? | -- | ||||||||
Do the purge valve and the vent solenoid click when commanded ON and OFF? | -- | |||||||||
Is the fuel tank pressure within the specified value range? | -0.32 - +0.32 kPa (-1.28 - +1.28 in. H2O) | |||||||||
5 |
Did you find and correct the condition? | -- | Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage or | |||||||
|
Important: : Before continuing with the diagnosis, zero the EVAP Pressure and Vacuum gauges on the J 41413 EVAP pressure/purge Diagnostic Station. Refer to the tool operating instructions.
Important: Do not exceed the pressure given in the first specified value. Is the fuel tank pressure at the second specified value? | 1.25 kPa (5 in. H2O) .96 kPa (3.85 in. H2O) | Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage or | ||||||||
7 |
Does the EVAP pressure return to the second specified value within 5 seconds? | 1.25 kPa (5 in. H2O) 0 kPa (0 in. H2O) | Go to Diagnostic Aids | |||||||
Does the vacuum remain below the second specified value? | 2,500 RPM 2.49 kPa (10 in. H2O) | |||||||||
9 |
Did you complete any repairs? | -- | ||||||||
10 |
Notice: The EVAP canister may have released carbon particles which caused this part to fail and may cause damage to other components. Check the EVAP canister for loose carbon before returning the vehicle to service. Did you complete the replacement? | -- | -- | |||||||
11 |
Notice: The EVAP canister may have released carbon particles which caused this part to fail and may cause damage to other components. Check the EVAP canister for loose carbon before returning the vehicle to service. Did you complete the replacement? | -- | -- | |||||||
Does the EVAP pressure return to the second specified value within 5 seconds? | 1.25 kPa (5 in. H2O) 0 kPa (0 in. H2O) | |||||||||
13 |
Does the DTC reset? | -- | System OK |
