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Home >> Jeep >> 2014 >> Wrangler Sahara, Standard Trans >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> 3.6L - DTCS P0157 To P0457 >> Diagnosis And Testing >> P0457-Loose Fuel Cap >> Theory Of Operation

Theory Of Operation

Fig 1: View Of EVAP System Components
GC0157500Courtesy of CHRYSLER GROUP, LLC
EVAP SYSTEM COMPONENTS
CALLOUT  DESCRIPTION 
1 Filter
2 ESIM Switch
3 Evaporative Canister
4 Fuel Tank Vent (Check Valve)
5 Control Valve
6 Inlet Check Valve
7 Fuel Tank Pressure Sensor
8 To Purge System
9 Fuel Fill Tube

Fuel level is recorded when the ignition key is turned off and is compared to the fuel level when the ignition key is turned back on. The Powertrain Control Module (PCM) recognizes an increase in fuel level and will fail the Large leak test because the fuel cap is broken or not installed properly. GAS CAP will be displayed to inform the owner that the cap is off of loose.