P0446

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The Evaporative Emission (EVAP) system is tested by applying vacuum to the 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 valve and the EVAP vent solenoid are turned on, allowing the engine to draw a small vacuum on the entire EVAP system. After the desired vacuum level has been achieved, the EVAP canister purge 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 valve, and monitoring the fuel tank pressure sensor signal. With the EVAP vent solenoid open, any vacuum in the system should decrease quickly unless the vent path is blocked.

The evaporative system includes the following components:
^ The EVAP canister
^ The EVAP canister purge valve
^ The EVAP service port
^ The EVAP vent valve
^ The fuel cap
^ The fuel pipes and hoses
^ The fuel tank
^ The fuel tank pressure sensor
^ The fuel vapor lines
^ The purge lines

CONDITIONS FOR RUNNING THE DTC
^ The following DTCs are not set: P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0452, P0453, P0502, P0503, P0601, P0602, P1621 and P1133.
^ The Barometric Pressure (BARO) is more than 75 kPa.
^ The Intake Air Temperature (IAT) is between 5°C and 29°C (41°F-84°F)at engine start up.
^ The Engine Coolant Temperature (ECT) is between 5°C and 29°C (41°F- 84°F) at engine start up.
^ The IAT is not more than 1°C (2°F) above the ECT at start up.
^ The ECT is not more than 7°C (12°F) above the IAT at start up.
^ The fuel tank level is between 26 percent and 74 percent.
^ The Throttle Position (TP) angle is between 7 percent and 35 percent.
^ The EVAP solenoid is at 40 percent PWM.

CONDITIONS FOR SETTING THE DTC
The EVAP system is unable to release the 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, the DTC acts like a type B diagnostic under certain conditions. 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 P0460, P0461, P0462 or P0463 is set along with an EVAP System DTC, the EVAP DTC cannot be considered valid until you repair and clear DTC P0460, P0461, P0462 and P0463.

Any of these conditions can cause DTC P0446 to set. Inspect the following components for the indicated conditions:
^ A poor electrical connection at the PCM. Inspect the harness connectors for the following conditions:
- Any backed out terminals
- Any incorrect mating
- Any broken locks
- Any improperly formed connectors
- Any damaged terminals
- A poor terminal-to-wire connection
^ A damaged wiring harness. Inspect the wiring harness to the following components for an intermittent open or short:
- The EVAP canister purge valve
- The EVAP vent valve
- The fuel tank pressure sensor

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
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.