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
GoTech Tips
Tip
: ESIM mounting angle effects system calibration, ESIM and canister mounting angle must not be modified
Tip
: It typically takes over a week for the small leak monitor to complete after repair