EVAP/drive cycle

[Rollybear1]

Hello everyone. Just picked up my first GMC. Its a 98 Sierra K1500 with the 5.7 Vortec. Nice truck! Very happy with the purchase. Im trying to get it emission tested (utah) and cant seem to get the EVAP test to complete.
No check engine light yet but the previous owner said it occasionally would set one for EVAP small leak.
Any advice on how to get it to complete the test? Ive driven it cold, highway speeds etc but still shows incomplete on that test only.
Thanks in advance for any thoughts or advice.

Dave

 

[stutaeng]

EVAP issues on these trucks are really uncommon. I've watched a few of the WellTech videos on YT on the to try to troubleshoot EVAP issues on my 06 GMT800 SUV, which are pretty common on those I've gathered.

Do you have a bi-directional scanner? I'm wondering if test shows incomplete because the system is detecting a small leak?

At least on the GMT800, the EVAP test is not performed when the gas tank is less than 15% or greater than 85%. That's how I've gotten mine to pass...by keeping the gas nearly full. I'm not sure if that's also true on the GMT400s though.

 

[Rollybear1]

My scanner is a plug in to the OBD and then an app on my phone. it shows mode 6 data.
Interesting, I didnt think about the fuel level but it makes since. Ill check but i know its up there, probably above 3/4.
Thanks stutaeng!