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EVAP System Override _ error fix


JF in NC
02-08-2017, 02:52 AM
EVAP system override

Check engine light for EVAP has been on for 5 years (04 Mitsubishi) To pass state inspection, have spent hundreds on multiple attempts to fix from multiple shops. Always told, can't find what's causing it and they want more money to find.

An EVAP error can be very dangerous if your fuel or fumes are leaking, so be sure to thoroughly check and try to fix before trying this.

I couldn't find a leak and the purge, vent, and pressure sensor all worked. So came up with a way to eliminate the error and enable the system to still purge the tank. this should work for any EVAP system.

In short I spliced in a pseudo EVAP circuit using a 12v valve, a barbed tee, and tubing.

To do this, I first removed the pressure sensor from the fuel tank, covered the hole by fabricating a plate out of sheet metal and gasket maker as the sensor will not be put back. I then inserted this pressure sensor into a piece of tubing. Held together using zip ties through a hose clamp on the hose. Still back near the fuel tank disconnect the hose from the engine vacuum purge valve and connect it to the tee with the pressure sensor. The third leg of the tee goes to the 12v valve (Amazon). You will need 2 barbís with pipe thread depending on your valve. The other side of the valve goes to where the vacuum purge line used to.

Now splice (not cut) the wires going to the vent valve for your vapor canister and connect to the 12v valve you installed.

Splicing the wires and connecting a hose between the valve you installed and the open side of the purge hose circuit will enable your vehicle to empty the vapor canister and avoid any errors due to expected emissions from purging the fumes. This will also be partially environmental friendly.

I had the p0042 error, but assuming your components are good, this should fix any EVAP circuit error.

This is not a simple fix but it works. Do not try to plug lines or disconnect or power any component as that won't work. The system needs to verify a vacuum is present, verify a vacuum is held with the purge off, verify the vacuum can be released with the vent valve, and does not build a vacuum when vent is re-closed with purge off. These combinations of component state is what makes this so difficult to trick the ECM.

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