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Evap Diagnostic Summary P0443 Purge Control Valve Circuit problem P0444 Purge Control Valve Circuit Open • P0445 Purge Control Valve Circuit Shorted • P0458 Purge Control Valve Circuit Low • P0459 Purge Control Valve Circuit High • P0496 Purge Control Va

ADMS, Inc. and Maximum Productivity Concepts, Inc.
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Evaporative Emission Control System Diagnostics
Contents
Evaporative Emission Control System Diagnostics ........................................................................................................ 1
Evap System Operation ................................................................................................................................................ 6
DTC Specific Diagnostics .............................................................................................................................................. 6
THINK SAFETY! ............................................................................................................................................................. 6
Evaporative Emission System Introduction ................................................................................................................... 6
Evap System Generations ............................................................................................................................................ 7
Enhanced Evap Systems ............................................................................................................................................... 7
Need for Improved Diagnostics ................................................................................................................................... 7
Statics of Evap System Failures .................................................................................................................................... 8
OBD Diagnostics ........................................................................................................................................................... 8
Equipment for Gas Cap Testing .................................................................................................................................... 8
Check for Codes ........................................................................................................................................................... 9
GM OBDI Example ....................................................................................................................................................... 9
Purge Solenoid Valve ................................................................................................................................................... 9
Purge Flow Sensor ..................................................................................................................................................... 10
Purge Vacuum Switch ................................................................................................................................................ 10
Purge Test Port .......................................................................................................................................................... 11
Evap Vacuum/Pressure .............................................................................................................................................. 11
Evap Test Port ............................................................................................................................................................ 12
Impact of 1 psi ........................................................................................................................................................... 12
Purge Rules ................................................................................................................................................................ 13
Purge Criteria ............................................................................................................................................................. 13
Leak Check Enabling Conditions ................................................................................................................................. 14
Ford’s Enabling Conditions ........................................................................................................................................ 14
Service Bay Evap Self-Test ......................................................................................................................................... 14
Service Bay Self-Test Example .................................................................................................................................... 16
Evap Service Bay test Data ......................................................................................................................................... 17
Monitoring Purge Activity .......................................................................................................................................... 18
Purging a Full Canister ............................................................................................................................................... 18
ADMS, Inc. and Maximum Productivity Concepts, Inc.
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Purge Action in Scan Data .......................................................................................................................................... 19
Initial Purge after Restart ........................................................................................................................................... 19
Initial purge Graph after restart ................................................................................................................................. 21
Diagnostics for All Systems ........................................................................................................................................ 22