Evaporative Emissions: Description: Description
| CALL OUT | DESCRIPTION |
|---|---|
| 1 | Fresh Air Filter |
| 2 | Evaporative System Integrity Monitor (ESIM) |
| 3 | Evaporative Charcoal Canister |
| 4 | Fuel Tank Vent (Check Valve) |
| 5 | Control Valve |
| 6 | Inlet Check Valve |
| 7 | Fuel Tank Pressure Sensor |
| 8 | To Engine Purge Solenoid and Intake Manifold |
| 9 | Fuel Fill Tube |
The evaporative emissions system is designed to control the release of fuel vapors into the atmosphere. The fuel tank check valve (4) and control valve (5) are used to reduce emissions due to the venting of vapor expansion within the fuel tank. When fuel evaporates from the fuel tank, vapors pass through a vent hose to the evaporative charcoal canister (3) where they are temporarily held. When the engine is running, the vapors are drawn into the intake manifold (8). In addition, fuel vapors produced during vehicle refueling are allowed to pass through the vent hose to the evaporative charcoal canister (3) for temporary storage (prior to being drawn into the intake manifold). The fuel tank check valve (4) and control valve (5) are non-serviceable components of the fuel tank assembly. The system is equipped with self-diagnosing capability using an Evaporative System Integrity Monitor (2). Refer to SWITCH, EVAPORATIVE EMISSIONS SYSTEM MONITOR, OPERATION .
The fuel tank pressure sensor (7) provides the PCM with information on vapor pressure inside the fuel tank. Excessive fuel tank pressure could cause fuel vapors to vent out the fuel filler cap or damage system components while insufficient fuel tank pressure (vacuum) caused by lack of fresh air entering the tank (1) to take the place of consumed fuel could lead to collapsed tank, lines or loss of fuel pressure.
The inlet check valve (6) prevents fuel from splashing back on the customer during vehicle refueling. This valve is also a non-serviceable component of the fuel tank assembly.
The PCM compares input signal voltages from each input device with established high and low limits for the device. If the input voltage is not within limits and other criteria are met, the PCM stores a diagnostic trouble code in memory. Other diagnostic trouble code criteria might include engine RPM limits or input voltages from other sensors or switches that must be present before verifying a diagnostic trouble code condition.