P0446

Schematic:

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 system is checked by applying vacuum to the EVAP system and by monitoring for a vacuum decay. The 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 (EVAP vent solenoid Open, EVAP purge PWM 0 percent), and 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 (stuck closed)
- The vent hose for the following conditions:
- Plugged
- Kinked
- Pinched
- 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
- No active MAP DTCs
- No active IAT DTCs
- No active ECT DTCs
- No active TP DTCs
- No active oxygen sensor DTCs
- No active fuel tank pressure DTCs
- No active VSS DTCs
- No active PCM Memory DTCs
- The BARO is more than 75 kPa
- The Start-up IAT is between 5°C and 29°C (41°F and 84°F)
- The Start-up ECT is between 5°C and 29°C (41°F and 84°F)
- The Start-up ECT is less than 8°C (14°F) above the Start-up IAT
- The Start-up IAT is less than 1.5°C (3°F) above the Start-up ECT
- The fuel tank level is between 15 percent and 85 percent
- The TP sensor is between 7 percent and 35 percent
- The vehicle speed is less than 70 MPH (113 KPH)
- The Purge solenoid is enabled

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.
- The EVAP purge function is disabled until the diagnostic passes.
- 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.
- A scan tool can clear the DTCs

DIAGNOSTIC AIDS
Check for the following conditions:
- Poor connection at PCM - Inspect harness connectors for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Poor terminal to wire connection
- Damaged harness - Inspect the wiring harness to the EVAP vent solenoid and the fuel tank pressure sensor for an intermittent open or short circuit.
- Kinked, pinched or plugged vent hose - Verify that the vent hose between the canister and the EVAP vent solenoid is not restricted.

Check for charcoal particles. Refer to Evaporative Emission (EVAP) System Cleaning before starting repairs. Evaporative Emissions System

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that causes the DTC to be set occurs. This may assist in diagnosing the condition.

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

TEST DESCRIPTION
The numbers below refer to the step numbers on the Diagnostic Table.
3. 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.
4. This step tests the fuel tank pressure sensor at the ambient pressure.
6. This step verifies that the fuel tank pressure sensor accurately reacts to the EVAP system pressure changes.
8. This step tests for a blocked EVAP canister.
12. This step duplicates the Powertrain On-Board Diagnostic test.