CEL... how long after clear to emission?

[Pike2350]

I had a CEL on my truck.....i've since fixed the issue (I believe)....how far/long do I need to drive to make sure the computer is ready to allow an emission test?

I hardly ever drive it and there are other issues not making ideal to drive right now. I just want to get it registered for when I do want to drive it to the trail...and my temp registration is expiring in a week....and I'm not sure how much driving I can do in the truck right now.

 

[UNSTUCK]

Pretty sure each rig is different. Last time I had to do this was in an Armada. We had to drive 50 miles before it was ready.

 

[moab_cj5]

If it is OBD 2, go to any auto parts store (Autozone) and have them clear the codes. You should be good to go after that.

 

[DAA]

If it is OBD 2, go to any auto parts store (Autozone) and have them clear the codes. You should be good to go after that.

I don't think that will work. I might have this wrong though. But my (possibly incorrect) understanding, is that simply clearing the codes does not set the "ready" state that an emissions test looks for. The only way to get that, I think, is to complete the necessary cycle to have some of the sesnors run long enough to go from trouble code set, to ready.

Both the cheap code reader I have, and the OBDII dongle/phone app I use (Torque) show the emissions ready state. Clearing codes doesn't reset the emissions ready.

A real world example I have experienced, is putting a new battery in too soon before an emissions test. The car had not thrown any codes, but disconnecting the battery does a reset similar to clearing codes with a reader or app. It showed emissions not ready on the first try. I had to drive it a couple days and bring it back.

I used to know the parameters of getting to emissions ready for my Jeep, but I have long since forgot. But it was x number of start and drive cycles, combined with x amount of time at normal operating temp for a couple of the sensors to normalize. In the case of my LX470 that got the new battery mentioned above, just driving it to and from work for three or four days total did it.

- DAA

 

[moab_cj5]

I don't think that will work. I might have this wrong though. But my (possibly incorrect) understanding, is that simply clearing the codes does not set the "ready" state that an emissions test looks for. The only way to get that, I think, is to complete the necessary cycle to have some of the sesnors run long enough to go from trouble code set, to ready.

Both the cheap code reader I have, and the OBDII dongle/phone app I use (Torque) show the emissions ready state. Clearing codes doesn't reset the emissions ready.

A real world example I have experienced, is putting a new battery in too soon before an emissions test. The car had not thrown any codes, but disconnecting the battery does a reset similar to clearing codes with a reader or app. It showed emissions not ready on the first try. I had to drive it a couple days and bring it back.

I used to know the parameters of getting to emissions ready for my Jeep, but I have long since forgot. But it was x number of start and drive cycles, combined with x amount of time at normal operating temp for a couple of the sensors to normalize. In the case of my LX470 that got the new battery mentioned above, just driving it to and from work for three or four days total did it.

- DAA

Good to know. I’ve always cleared codes when they’ve come up, and never had an issue.

 

[Toad]

DAA is correct. 1996 thru 2001 are allowed two not readies. 2002 thru current are allowed 1 readiness monitor to not have set. I have heard that the current standard for 2017 or 18 do not allow 1 readiness monitor. They all have to be set. There is no magic number to reset everything. I have seen cars take several hundred miles to be ready.

 

[TurboMinivan]

DAA is correct. 1996 thru 2001 are allowed two not readies. 2002 thru current are allowed 1 readiness monitor to not have set. ... There is no magic number to reset everything. I have seen cars take several hundred miles to be ready.

This is spot on, and I just experienced it personally with my new-to-me 1997 Geo Metro. I bought it for pocket change with a non-functional throwout bearing and a CEL. Right after I did, my friend Mike bought a '00 Metro of his own, also with a CEL. Our CELs were for the same issue, so we fixed them simultaneously and cleared the fault codes. There were no new codes and no pending codes, but we did need to put them through a readiness drive cycle in order to pass the smog test. Lucky me, I drove it from Orem to Lehi on State Street and, without knowing, more or less replicated the perfect drive cycle. The next day I drove it to work and only had one monitor not ready, so I passed my test easily.

Mike would not be so lucky. After his first drive to work the next day, he still had four monitors not ready. He had to drive back and forth many times over the course of a week for two of them to set (one at a time, very stubbornly) so that, at last, he could pass his own test. It only took me about ten miles before I was good to go, whereas he must have put over a hundred miles on his car to get to the same point. Oh, well.