Evaporative System Integrity Monitor (ESIM) System

Components

• A Purge solenoid is used to purge fuel vapors and pull system into vacuum for leak detection
• A EVAP Charcoal canister is used to absorb and store fuel vapors
• A ESIM assembly is used to monitor the system for leaks
• A Fuel Tank Pressure sensor is used for secondary component testing

System Leak Test Operation

• The ESIM conducts tests on the evaporative system as follows: An engine off, non-intrusive test for small leaks and an engine running, intrusive test for medium/large leaks
• To start the key off, non-intrusive testing, the engine control module (ECM) cycles the purge solenoid to equalize the system
• The normally closed system will then naturally draw into a vacuum as the fuel and air in the system cool
• After it reaches -1 In H20 the internal ESIM switch closes signaling the ECM the test passed
• If the switch doesn't close in the allotted time, the ECM will log it as a leak test failure and run the intrusive medium/large leak test
• The intrusive test still monitors the ESIM switch, except it uses the purge solenoid and manifold vacuum to pull the ESIM switch closed
• The ECM then monitors how long it takes for the vacuum to decay and the switch to open up and compares to internal calculations to determine if a leak is present

Basic Diagnostic Checks

• Inspect for loose Gas cap
• Inspect hoses for cracks, leaks and proper routing and attachment
• Check purge solenoid function with scan tool or jumper wires
• Check purge solenoid for mechanical leakage
• Check ESIM switch Circuits
• Check ESIM internal switch with vacuum pump
• If all checks pass, smoke/flow testing is required
• Block EISM filter port to seal system for smoke/flow testing

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