EVAP system test description

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

The EVAP system test finds gas leaks or blockage of EVAP system using the changes of the fuel tank pressure.
- This test starts after sending an on-demand test signal from the M-MDS to the PCM.
- This test consists of three stages, and each stage is performed automatically as follows:
  Stage 1 test. (Test for large leak or blockage)
  - M-MDS send the stage 1 test start signal to the PCM.
  - PCM controls the CV solenoid valve and purge solenoid valve to control the tank pressure to the targeted value.
  - M-MDS detect the large leak or the purge line blockage if the tank pressure does not arrive at the target vacuum in specified period.
Fig 1: Identifying Fuel Tank Pressure (Large Leak Or Blockage)
Courtesy of MAZDA MOTORS CORP.

Stage 2 test. (Test for small leak)

When fuel tank pressure arrived at the targeted pressure at stage 1 test, M-MDS send the stage 2 test signal to the PCM to turn off the purge solenoid to keep the tank pressure.
M-MDS detect the small leak if the tank pressure can not keep within the target in specified period.

Fig 2: Identifying Fuel Tank Pressure (Small Leak)

Courtesy of MAZDA MOTORS CORP.

Stage 3 test. (Test for blockage)

M-MDS send the stage 3 test signal to the PCM to turn off the CV solenoid for check the blockage of EVAP system.
M-MDS detect blockage of the CV solenoid valve or air filter if the tank pressure does not arrive at the target (atmosphere).

Fig 3: Identifying Fuel Tank Pressure (Blockage)

Courtesy of MAZDA MOTORS CORP.