EVAP leak test?

[Deano Garrett]

I am working on a 2001 Chevy Blazer 4.3l 2WHD, and using a LAUNCH CRP129 scanner. Also a homemade smoke machine(small pump, paint can, ect). Now I had codes P0300 and P0171 to start with. Found small intake leak(fixed it), then when smoke tested found small leak in the filler neck tube(fixed it). No more leaks I can see and when I run the EVAP leak test w/KOEO it reply’s PASS, but when I run EVAP leak test w/KOER it reply’s FAIL. Also after trying to run drive-cycles for the readiness monitors to set it seams to get stuck at the EVAP and SECONDARY AIR monitors(doesn’t fail them but doesn’t complete them, just remains at INC).
Anyone who maybe is familiar with these GM systems maybe could help shed a little light on if I still have a issue or any help would be great, THANKS

Topic

[college man]

See if this helps. What other dtc are you getting or did get?

http://www.justanswer.com/chevy/14vns-2001-chevy-blazer-auto-smoked-system-i-repaired.html

[Deano Garrett]

OK, first off THANKS college man, and as far as codes pre-repair there was P0400 and P0171 post repair there are no set or pending codes being displayed. Have replaced fuel cap repaired filler neck leak and replaced intake gasket because of leak. Smoke test with vent commanded shut shows no leaks, but when KOER it says EVAP leak test failed but still no set or pending codes. So maybe the scanner is saying failed because it hasn’t run the monitor yet(IDK). And I know it wont run the monitor if it fails something prior to time to run the monitor. I am just at a loss as to what might be causing it to fail and prevent the monitors from running, the car runs great and cold starts you can hear the SecAir pump running along with good short and long term fuel trim numbers( cold 3.4%stft 7.8ltft-warm 0%stft 7.3%ltft on average).
And just a little fyi that is my problem, is that the car has expired tags and DMV won’t extend any more moving permits to him so that makes it allot more fun trying to drive-cycle this car.Really burns my hide when people get the first 30 day permit and then wait till the last 2 days of it to bring it in. But like I said that is my venting.

[Its me]

FWIW some EVAP system monitors have to have the car with 1/4 to 3/4 tank full to execute properly I believe GM is (15% to 85%) as well as the IAT reading between a certain temperature (39 to 86 degrees F).. I believe also some may have to have a few cold starts for the drive cycle… These numbers are from my fuzzy memory and ballparking them.. May want to check the vehicle drive cycle specs on this and check the fuel level and IAT….

-Karl

[Author]

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