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Old 11-04-2019, 06:18 PM   #1
Scooby Newbie
Member#: 485056
Join Date: Apr 2018
Default Trick EVAP System Leak Detection - 2004 WRX

Hello all,

I have a 2004 WRX and I am looking to delete my EVAP system, however there is one thing holding me back at the moment. Accordingly, the ECM runs a check that does the following:

Mode A (Evaluation of EVAP. generation amount)
Calculate the tank pressure change amount (P1).

Mode B (Negative pressure seal)
Introduce the intake manifold pressure into the fuel tank, and reduce the tank pressure to the target pressure.

Mode C (Pressure increase check/premature OK judgment)
Wait until the tank pressure returns to the target value. If the tank pressure does not return, perform the premature OK judgment.

Mode D (Negative pressure change amount measurement/EVAP. leakage diagnosis)
Calculate the tank pressure change value (P2), measure the diagnosis value using P1 calculated in Mode A. Perform the EVAP. leakage diagnosis using the diagnosis value.

Mode E (Drain valve property abnormality diagnosis)
Perform the drain valve property abnormality diagnosis depending on the magnitude of the tank pressure change after the leakage diagnosis completed.


I was initially thinking of using some resistors in place of the removed Pressure Control Solenoid, Drain Valve, and Purge Control Solenoid Valve. But with the added knowledge of this diagnostic check, I don't think this will work.

I'm wondering if a resistor in place of the fuel tank pressure sensor will help trick the ECM into thinking there are no leaks.

Unfortunately tuning the codes out is not really an option because I'm using the Accessport.

Any thoughts? Any help is greatly appreciated!

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