EVAP Leak Check System Description
ECM boots up EVAP leak check system after 5 hours from ignition switch off and ECM starts EVAP leak check by operating EVAP leak check module (1).
EVAP leak check module consists of EVAP leak check pressure sensor (2), EVAP vent valve (3), EVAP leak detection pump (4) and reference orifice (5).
ECM (17) executes EVAP leak check by the following step.
- Barometric Pressure Check:
ECM measures barometric pressure (P0) by EVAP leak check pressure sensor while EVAP vent valve is opened (OFF) and EVAP leak detection pump is not operated (OFF).
- Reference Pressure-1 Check:
ECM measures vacuum as reference pressure-1 (P3) which is generated by EVAP leak detection pump through reference orifice (equivalent of 0.5 mm (0.02 in.) diameter hole) while EVAP vent valve opened (OFF) and EVAP leak detection pump operated (ON).
- Leak Detecting Pressure Check:
ECM measures vacuum as leak detecting pressure (P5) while EVAP vent valve is closed (ON) with EVAP leak detection pump operated.
- Reference Pressure-2 Check:
After operating EVAP canister purge valve from close to open then close, ECM measures vacuum as reference pressure-2 (P8) which is generated by EVAP leak detection pump through reference orifice while EVAP vent valve opened (OFF) and EVAP leak detection pump operated (ON).
- EVAP Leak Check:
ECM compares reference pressure-2 (P8) to leak detecting pressure (P5). If leak detecting pressure (P5) is higher than reference pressure-2 (P8), EVAP system contains a leak which is greater than a leak caused by a 0.5 mm (0.02 in.) diameter orifice.