Emissions - EVAP Emission Control Diagnosis for P0446

Group: FUEL SYSTEM

Number: 06-30-005

Date: NOVEMBER, 2006

Model:
2001-2005 XG300/350,
1999-2005 2.4L SONATA,
2001-2006 2.4/3.5L SANTA FE

Subject:
ENHANCED EVAPORATIVE EMISSION CONTROL DIAGNOSIS AND REPAIR FOR P0446

THIS BULLETIN SUPERSEDES TSB 04-30-001 TO INCLUDE ADDITIONAL VEHICLES.

DESCRIPTION:

Diagnostic trouble code P0446 (Scanner Description: EVAP System: Vent Control) sets when the fuel tank pressure sensor measures excessive vacuum in the fuel tank.

P0446 is NOT related to a system leak. The Hi-Scan EVAP LEAK CHECK will NOT check for a P0446.

NORMAL SYSTEM OPERATION:

In an evaporative emissions system, fuel vapors and air in the charcoal canister are drawn into the intake manifold through the canister purge valve. The vapor/air drawn from the charcoal canister is replenished by fresh air being drawn through the EVAP air filter and canister close valve. Normally, there is a small but measureable amount of vacuum at the differential pressure sensor during purging.

During the system leak check (the vehicle must be driving at a steady speed over 1800 RPM), the canister close valve shuts and purging occurs until the system is drawn to 1.8 volts (measured at the differential pressure sensor). The vacuum will remain at 1.8 volts for up to 30 seconds (depending on the fuel level). This is NORMAL operation, and should not be confused with the diagnostic procedures described later.

In a system that sets P0446, the amount of vapors being purged from the canister is greater than the volume of fresh air entering into the canister. This causes the canister to build up vacuum. When the canister increases in vacuum, the remainder of the system (fuel tank, hoses, separator, etc.) will also increase in vacuum. The fuel tank pressure sensor measures and reports the vacuum level (in volts) to the ECM. If the vacuum level reaches beyond the ECM threshold, P0446 is set into ECM memory. If this condition occurs on two consecutive drive cycles, then the Check Engine" light will illuminate.





EVAPORATIVE EMISSION COMPONENTS











P0446: TROUBLESHOOTING TREE