The monitor will run its tests, and complete the diagnostics, (monitor will complete) when the drive patterns have been duplicated as described in the drive cycle, and all other requirements are met, (fuel level is correct, no DTC's in memory, etc etc).

When the monitor checks for leaks, the PCM closes the EVAP vent solenoid, (near the vapor canister), and applies a given amount** of vacuum to the EVAP system by momentarily opening the purge solenoid, (right side of intake manifold, near ignition coil). This is called a purge and seal. The fuel tank pressure sensor measures the amount of vacuum in the system. The PCM "watches" how long it takes for the vacuum to decay. Depending on how long it takes, if it's too rapid, the PCM will set one of three DTC's, large, medium, or small leak.


**This is where fuel level in the tank comes into play. Less fuel means the purge solenoid needs to remain open longer to "pull" (apply) vacuum on the EVAP system. With more fuel in the tank, the solenoid doesn't need to remain open as long. This is why the fuel level sender, and the pressure sensor, must be working properly.


This is just one of several tests in the EVAP monitor. Like I said, this is a tough monitor to run and complete, and it might take a while. You know exactly what you have to do, and you've gotta be coming very close to duplicating the pattern. Now you see why it can take so long for the "average driver" to complete it.

 

Yes Captain it just so happens I have one I got for a gift without abs and one with abs I bought for my current blazer.Both have yellow light on with the evap monitor blinking.

 

Are they both Innova? We're looking for an unbiased second opinion

 

Yes there both Innova but I will go to the parts store and have them use there acuscan and let you know what it reads.

 

captain what do you think about the answer I got from the ase approved tech.
06 January 2016 03:51
Dr.Carz
Chevy Mechanic
Well the fuel level must be between 1/4 and 3/4 full and the system will require and over nite soak or 2 this time of year when it gets cold it gets harder to run. It will pull a vacuum and the after 8hr soak or so will pull info on start up. If you have access to scan tool that can perform a purge and seal or evap test will help this monitor along. Here in NY you can have 1 not ready and pass Inspection. Good luck hope this helps driving for miles and miles will not help.Please remember to rate my service and Accept Thank You.

 

Captain what do you think about what Dr.Carz had to say Its much safer than the drive cycle on the freeway yesterday some guy flipped me off and passed me on the right even though I had put on my four ways don't usually use then or blinkers because worried it will cancel the drive cycle but when coasting down to 20 mph It seems to be the safe thing to do especially if there are cars behind you when your coasting down.Even in the right lane.

 

This reminds me of a kid playing Mama against Papa. Just pick one specialist that you believe in and do what he asks. Don't ask one to expain what the other one says about a car that neither one has seen.......

Go back and read post #2. If it's not completing the tests there are two possibilities:

1. You are not doing the drive cycle correctly
2. There is some fault present that prevents the drive cycle from completing.

In post #1 you said there was no hard code in memory. Does that imply there was a pending code?

 

No and I am sorry if you think that's the case because the true fact is I just want to pass the emission test.Nothing more nothing less and I have tried the gm drive cycle about 8 times and I think I got it down unless it don't allow time between warm up and freeway cycle and if that's the case the only way to pass the drive cycle is with a dyno first start in the morning or park your car on the freeway over night then start test fresh and right after warm 2 1/2 minutes everything electrical on. Accelerate to 55 mph for 3 minutes coast down to 20 mph accelerate to 55 for 5 minutes coast down to 20 no brake gears and maybe even no four ways don't know.Do you.

 

Ok Lesmyer didn't mean to insult any feelings but I took the advice of trying a different scanner went to ORiley's used there Bosh tester and it said that the evap hasn't run complete with a extra code po102 mass or volume circuit low input.Now I know what and were that is I bought some cleaner for it first.And when I did the manifold gasket I removed that and the complete air box system for extra room when doing the lower intake gaskets and benched it then when finished put in fresh oil and filter and new antifreeze also new air cleaner element. Don't know if that had anything to do with the pending code or if it was just due 100000 miles now.2003 gm blazer l/s 4.3 liter

 

This is to you Captain thank you for all your help.But tonight with that new code and the evap still not running it got me to thinking of when I took off the complete cold air box and all to get extra room to remove the lower intake to replace the gaskets.And you know it dawned on me tonight the code low censor input that's low air input.When I removed the cold air input box the little extension
must have fell between the headlight and the front end because I looked down but didn't see it between the air box and the front end and sure enough no plastic exstention at all my guess would be it fell on removal of the filter box in between the headlight and the front end.So I guess I will be passing that emissions after all,and again thank you for all your patience.