GM OBD II Clear Evap and Secondary Air Monitors in ECU 

I did this at about this time last year. The temperature difference in Prescott made the difference. When I came out from the hotel at about 6:30 a.m. it was cool, probably in the 60's and the engine had cooled overnight so that was enough to get a cold start and it reset the EVAP codes. The guy at Apex told me I would never get the codes to clear in Phoenix because it was just too hot to get a good cold start at this time of year and he was right.

@@bradmorgan911 I actually called the guy at Apex and he told me to come in and get it diagnosed before telling me to go up to Prescott. Apex has amazing reviews so I might be using them more often

@@Theyallknow_Ella That's cool. Not sure if there is any difference in our cars' symptoms but when I told him mine he just said I needed to do the Prescott run. I'm sure those guys will fix you up. Good luck!

Take your Mass Air Flow out and clean it with Mass Air Flow cleaner from Auto Zone, is called CRC Mass Air Flow & Throttle Body Single-Use Cleaner and drive for 10 miles believe me it will clear the EVAC not ready in a second.

Joe, I'm no expert on this stuff for sure. I just did the drive cycles and then called the emissions shop when I couldn't clear the evap codes. I'd suggest calling Apex Automotive in Phoenix. Those are the guys I called and they broke the code for me and were extremely helpful even though they knew I wasn't bringing my car in and they weren't going to make money off of me. I was very impressed. www.apexautoaz.com/

One more thing I thought of. Did you let the car cool completely up at Big Bear before doing the cold start? It takes hours for the car to cool enough to get the cold start because the engine has to be within 10 or 11 degrees (I think) of the ambient temperature, so if you just let it sit for an hour or two you probably didn't get the cold start needed to reset the codes.

Yup. Fellow Texan here. Replaced my starter before getting it inspected. Can't get the Cat and Evap to be ready. Almost up to 300 miles later and still not ready

I have a cheap Harbor Freight scanner ($30 I think) and I also have an expensive Autel Scanner that I bought a couple of years ago because it is one of the few scanners that can actually reset the airbag light on a Porsche. That's the scanner I used for my Firebird when I did the drive cycles, so I am not positive but I think a cheapie scanner like the Harbor Freight one would work fine for a non-exotic car. You just need something that will capture the emissions data and codes and I think all the scanners are capable of that. If I had to do this again I would take the advice of one of the commenters below and would have put my car on jackstands and ran it through the drive cycles in my garage instead of out on the highway. After the 3rd or 4th cycle, it was really a PITA. Slowing to 20 MPH without using bakes or clutch takes a long time!

OH WELL THAT HELPS A LOT JUST DRIVE SOMEWHERE COLD. IF YOU LIVE IN TEXAS JUST DRIVE UP TO MINNEAPOLIS ITS ONLY HALFWAY ACROSS THE COUNTRY NO PROBLEM. REAL HELPFUL.

It is pretty simple. If you just drive your car normally, at some point the ECU will register the required drive cycles but it could take a while, sometimes even hundreds of miles. This is the way to do it quickly.

@@bradmorgan911 yes but we don’t all have the option to wait. We need to smog our truck so we can register it and it’s hot here in Vegas. You shouldn’t have to take a vacation to reset the gauge

@@SWilliams-01 what kind of truck do you have? I'm in california and cant pass smog,since september. i have a 2021 2500hd disel.

Depends on the model , some people also say u have to go 35 then come to a complete stop before accelerating to 55, google drive cycles for your particular make and models my Chevy gmc is different than other vehicles

I live in Sun City West so the drive was about 90 minutes for me. It wasn't the drive that made the evap codes go away. It was the cold engine start. The ambient temperature was too warm here in Sun City West to get a cold start so the computer would clear the codes. I drove to Prescott strictly to let the car sit overnight and then get a cold engine start the next morning because it is much cooler in Prescott. My guess is the codes cleared as soon as I did the cold start of the engine for my drive home.

@@bradmorgan911 Thanks. i was finally able to clear the secondary air. Started engine when outside temp was at 65F degrees . ECT was at 66F. and IAT at 64F. Idled for 2.5 minutes. Drove to freeway and slowly accelerated to 55 mph for 3 minutes. exited freeway and did some city driving for 5 miles. Jumped back on the fwy and slowly accelerated 55mph for 3 minutes. Got home and 2nd AIR cleared. 😃

@@rondela7341 Great to hear!

This sounds like a good idea. I will give it a shot

Don't remember if this is the website where I got it but here's one site where you can find it. In the first article near the top of the page click on "See More" and then scroll down to middle of the page and the chart is there www.justanswer.com/car/29acz-2001-olds-aurora-obdii-catalyst-evap-i-driven-350-miles.html

I did it 2 or 3 times in one day. But all that didn't matter in the end. It was the cold start that I needed to get the final monitors to clear and I couldn't get that in Phoenix in August. So when I drove to Prescott, spent the night, came out early the next morning when the temp was in the 50's and started the car, that did the trick. When I got back to Phoenix the final monitors had cleared.

You might want to call the folks at Apex Automotive and Emissions in Phoenix. That's who I called and who told me to drive the car to Prescott and get a cold start early in the morning. The guy there was great and told me exactly what to do and didn't try to get me to bring the car in so they could charge me.

Are you going to drive to Prescott? Please let me know if that works so I can make the trip up there

I was told I needed to start the car when the ambient temp was no more than 65 degrees. Don't know if that's accurate but I know I tried to start it here in Sun City West early in the morning when the outdoor temps were in the 80's and it didn't work. Plus, you need to make sure the ambient temp and coolant temp are within 10 degrees of each other for the computer to register a cold start. So you couldn't run the car and then park it for 30 minutes and try to start it (even if the ambient temp was low) because the engine would still be too hot. I went to Prescott and let the car sit overnight and then came out at about 6 a.m. when the outside temp was about 60 degrees and I started the engine, let it idle for a couple of minutes and then drove back to Sun City West and the evap monitors cleared.

@@bradmorgan911 👍🏼 Well that makes sense. Gonna have to give it a shot, can’t get the evap monitor ready on my Chevy cobalt.

@@drillsergeant623 Good luck. If you still have issues after you do the cold start I suggest you call the folks at Apex Automotive and Emissions. They were super helpful and walked me through this instead of telling me to bring the car in so they could charge me for driving it to Prescott and back. I did exactly what he said and the monitors cleared so he knew what he was talking about.

Great idea. That probably would work for everything except the Evap and Secondary Air System codes I was getting. For that I needed a cold start and then running through a drive cycle or two. I couldn't get the cold start here in Phoenix because it was summer time so I had to drive to Prescott, spend the night and then come out and start the car early the next morning when it was cold. Once I did that, the codes reset on my drive back to Phoenix.

LOL!!!! Genius! I have to do this drive cycle 5 times to my GMC Acadia...thanks!

That's a really good idea. People treat you like you're doing 20 when you're doing 55mph.

It was my fault for not knowing better. I bought the car and then we had a family emergency and had to fly out of state before I had a chance to register the car. I knew we would be gone for several weeks so I disconnected the batteries in our cars and naturally that cleared the ECU in each car. When we got back I connected the battery in the Firebird and took it to the emissions station without thinking and within 30 seconds the testing agent told me he was done and my car was "not ready", obviously because the computer was clear. I guess people used to be able to pass emissions by disconnecting the battery to clear any error codes and then going to have the car tested. Not anymore. Anyway, I could have just driven the car for 2 or 3 weeks and over time the computer would have reset itself but I wanted to get it registered quickly, so I went through the drive cycles to reset the computer. My lesson learned is never disconnect the battery within 30 days of taking the car for an emissions test.

Yep .its a little BS goverment game.so people get tired and Keep getting in deth with a new car.not me lol.i rather spend 500 once AND not have a 500 payment for 60 months.

It was easy for me to find out I needed to do this. I went to the emissions station to get my emissions certificate and the car failed and the fail notice told me exactly what was wrong. So if you don't need to have an emissions inspection done and your car is running fine you have nothing to worry about. I needed to pass the emissions inspection to register my car.

You just aren't supposed to downshift. Just let the car coast. I just pushed the clutch in and kept my foot off the brake and let the car coast until it got to 20 MPH. I would take the advice of someone else who commented on here and put the rear of your car on jack stands and then just do the drive cycles right in your garage. I should have done that instead of actually driving out on the highway. Would have been a lot easier.

@@bradmorgan911 Hey, thanks for your quick response. It's almost midnight & I'm thinking of going out now. How long does it take to decelerate to 20mph from 55mph because I hate to have to "ride" (push in the clutch for a long time). Can I actually shift to neutral and let go of the clutch until it gets to 20mph and then step on the clutch and shift into say 3rd gear and accelerate? Sounds kinda dangerous to me doing it on jack stands.

@@enufots4621 Sorry, I should have said just put it in neutral. I didn't hold the clutch in the whole time. I put it in neutral and let my foot off the gas. It takes quite a while to slow down to 20 MPH when you don't touch the brakes and don't downshift, unless you are going uphill. I was on a level road and it seemed to take forever to slow down.

@@bradmorgan911 Fyi, my car is not a GM but a BMW. All the other monitors were completed before I jumped on the freeway. Only the Catalyst was incomplete. I jump on the freeway about 12:30a.m. (no traffic) & drove about 8mins between 50 & 60mph. I stayed on the right lane and unfortunately due to the California fires they had extraneous road hazard lights (it was smokey) and I ended up exiting the freeway. I let go of the gas to let it decelerated, stepped on the clutch for a little while and shifted to neutral and no choice but to step on the brakes when i got to the bottom of the exit. Jumped on the freeway to head back home and tried to do the same. I had a ODB-2 adapter hooked up with the Torgue app running on my cell phone monitoring the emissions all this time. I wasn't sure if it was live data. Anyways, 7 mins into the drive the Catalyst was completed. Yeah, all green. Will try smog tomorrow. Thank you for you help!

@@enufots4621 That is awesome! Glad it worked for you. Good luck on the emissions test!

I didn't do a drive cycle when I left Prescott, or at least I didn't do it intentionally. The shop I called said I just needed a cold start to clear the evap codes so I just started the car early in the morning when it was cool and then drove from Prescott to Phoenix on I-17 and the codes were clear when I got home.