Theory Of Operation
| EVAP SYSTEM COMPONENTS | |||
|---|---|---|---|
| CALLOUT | DESCRIPTION | CALLOUT | DESCRIPTION |
| 1 | Filter - Fresh Air Inlet | 11 | Recirculation Tube (metal portion) (FTPS to Fuel Filler Tube) |
| 2 | Filter Hose (Filter to ESIM) | 12 | Gas Cap or Cap-less Refueling Unit (if equipped) |
| 3 | Evaporative System Integrity Monitor (ESIM) | 13 | Fuel Filler Tube |
| 4 | Evaporative Charcoal Canister | 14 | Multi-Function Control Valve (MFCV) in the Fuel Delivery Flange |
| 5 | Canister Tube (Fuel Tank to Canister) | 15 | GVV Tube (GVV to MFCV) |
| 6 | Purge Tube (Purge Solenoid to Canister) | 16 | Grade Vent Valve (GVV) |
| 7 | Purge Solenoid | 17 | Fuel Tank |
| 8 | Manifold Hose (Purge Solenoid to Engine Manifold) | 18 | Inlet Check Valve (ICV) |
| 9 | Recirculation Tube (Fuel Tank to FTPS) | 19 | Hose - Fuel Filler Tube to ICV |
| 10 | Fuel Tank Pressure Sensor (FTPS) | - | - |
PURGE FLOW MONITOR: The operation of the Purge Solenoid and evaporative purge flow is monitored using inputs from the Fuel Tank Pressure Sensor. The Purge Flow Monitor will only run if the previous engine off Small Leak event was a pass. The small leak diagnostic can only verify that the fuel tank system is sealed while the purge valve is closed. Therefore, it cannot be determined if the purge line between the solenoid and Intake Manifold is pinched or leaking. The Purge Flow Monitor is needed to verify these failure modes. The Purge Flow Monitor works on the premise that as flow through the system increases, so does the pressure drop in the system. The PCM monitors the Fuel Tank Pressure Sensor and looks for increasing vacuum in the Fuel Tank with increasing purge flow. Conversely, it looks for decreasing vacuum in the Fuel Tank with decreasing flow.
- The non-intrusive purge monitor runs during normal operation once the enable conditions are met and looks for a calibrated increase in vacuum in the fuel tank with increased purge flow, referred to as side 1. If side 1 passes, the purge monitor looks for a calibrated decrease in vacuum in the Fuel Tank with decreasing purge flow, referred to as side 2. If side 2 passes, the purge monitor is complete. If the purge flow monitor fails either side 1 or side 2, or does not complete both side 1 and side 2 within a specified time, an intrusive test is initiated to verify the results from the non-intrusive test.
- The intrusive diagnostic increases and decreases the purge flow in a more controlled manner to allow a more accurate test result. If the PCM detects a failure during the intrusive test, a purge system performance fault is set (P0441).
Only the Fuel Tank Pressure (FTP) Sensor is used for Purge Performance diagnostics. The ESIM Switch is not used for diagnosing the purge system.