Can HP Tuners tune out EVAP system?

[Rob Bell]

My issue is that I have the P0440 EVAP error code. I will try to fix it, but if it ends up being something where I may have to take it in and have the tank dropped or something really expensive, I am considering tuning out the EVAP system since it does not affect performance. I worry that as the car gets older, more and more of these non-essential systems will throw codes and drive me nuts.

I already have the after-cat O2 tuned out from a mail-order tune. We know the EGR can be tuned out. Can EVAP be tuned out too? What other systems can be tuned out?

[Watazz]

Re: Can HP Tuners tune out EVAP system?

if it is a p0440 it is more tha likely a vacuum leak. Yes Hptuners can tune it out. What I suggest you do is block off the vacuum that feeds the EVAP system though. Then for the p0440 code set it to no MIL light.

[MegaHertz]

Re: Can HP Tuners tune out EVAP system?

From what I'm reading you can tune out evap codes with HP Tuners. (seems to be able to disable a lot of codes or be able to change settings so it will never be set) I had a p0441 recently. Not same code but also evap. Turned out to be the vac line going from the throttle body to a piece of the evap system had come out. Not sure if that piece is the sensor or the soloniod (or both?). Replaced vac line and code was not pending after last drive.

[MegaHertz]

Re: Can HP Tuners tune out EVAP system?

If you want to look for it that line it is originally a hard plastic line that goes from the TB around the alt to the sensor/switch/solenoid (not sure which it is) behind the tb mounted on a bracket near the pass side valve cover. I replaced mine with a flexible hard plastic line - but will be replacing soon with new rubber hosing as the setup I have now isn't quite long enough.

[MegaHertz]

Re: Can HP Tuners tune out EVAP system?

sorry its behind the alt - not the TB

[Watazz]

Re: Can HP Tuners tune out EVAP system?

Even if it is a leak and you fix it you may still idle wierd. Because the vacuum hose runs all the way back to the tank. I had a leak somewhere above the tank and it caused my boost gauge to "jiggle" and I had a somewhat lumpy idle.

[MegaHertz]

Re: Can HP Tuners tune out EVAP system?

I have noticed some irregular idling myself. I recently fixed a rotted rubber coupler under the drivers side rear passanger area as well as this. I have yet to pull the panel on the rear wheel and inspect the canister as I get a gas smell when hitting corners with more than half tank. Thinking either the fill tube or the evap lines are messed up back there too. No codes tho from that.

[Watazz]

Re: Can HP Tuners tune out EVAP system?

gas smell could also be the pump seal.

[MegaHertz]

Re: Can HP Tuners tune out EVAP system?

do you mean the fuel pump access on the top of the tank? I may have to cut myself an access hatch if canister inspection proves the evap isn't the cause of the gas smell. I doubt I will be able to get the tank dropped with the amount of rust i have back there.

[Watazz]

Re: Can HP Tuners tune out EVAP system?

Yea the seal on top of the tank. And the tank is a super PITA to drop out. Just cut the access panel if the evap proves to be non problematic.

[Rob Bell]

Re: Can HP Tuners tune out EVAP system?

I'm going to start checking vacuum lines for cracks and such, and also that canister too. The cover plate has been hanging half loose for a couple of years now anyway. I keep forgetting about it, but now will be a good opportunity to fix that, too.

[Rob Bell]

Re: Can HP Tuners tune out EVAP system?

One thing I was thinking.... Supposedly the P0440 code is for a "large leak", maybe the gas cap. I was thinking that to test the bad-gas-cap theory, I could take off the cap and seal the filler neck with cellophane and rubber bands to see if the system then hold vacuum. If the light turns off I then know it's the gas cap. If the light stays on, it does not necessarily mean a good gas cap, but it may resolve the issue. Thoughts?

Is there a way to actually test the gas cap?

[ssms5411]

Re: Can HP Tuners tune out EVAP system?

You can test the gas cap after ruuning the car the cap should be pressurized so it should make a hizzing sound if you open it.

[Hib Halverson]

Re: Can HP Tuners tune out EVAP system?

You can disable any DTC with HPTuners, but...as others have stated, sometimes evap problems will also affect idle stability.

Also, if you live in a state which emissions tests, watch out because many "smog checks" include a test of the evap system.

My suggestion is to repair the evap system using the troubleshooting info in the factory service manual.

[Rob Bell]

Re: Can HP Tuners tune out EVAP system?

So here's an update on this one. I finally took the car in to the dealer for a diagnostic because I got the Reduced Engine Power code and light. For that one the accelerator pedal assembly has to be replaced, so I'm going to see about ordering it from GM Parts Direct and do it myself. The P0440 code is because the EVAP solenoid on top of the tank is not working, which would require removing the tank. This is a $600 repair for a $34 part. I'm still tempted to invest in HPT to tune this out. I'm investigating to see if HPT can safely tune this out, or if the emissions test will look for this and fail the car if it cannot find it. It may be a few more months before I go anywhere on this, because I want to save up the money for either HPT or the repair. The pedal thing is more urgent, even though it has not re-thrown the code. But I've been warned, and I'm afraid that thing could fail and leave me stranded.