We’ve touted code readers before. If you own an OBD-II-equipped (read: post-1996) vehicle, these little black boxes serve as the skeleton key to the check engine light (CEL) cellar door. But this weekend I was patching my F150 back together after getting it stuck in a friend’s lake of a back yard, and I discovered another great reason to own a code reader: the pre-emissions check.
In Texas, we have to get our vehicles inspected each year, and part of the inspection involves plugging the vehicle into an over-sized code reader — which checks to see if the car’s computer has detected any failures related to emissions. Since my truck’s due for inspection, I was concerned about the CEL. And rightfully so: When I jacked in the reader, I discovered the CEL was caused by — wait for it — an evaporative emissions failure.
Now since this light came on right after I left the truck running while up to its frame in mud for a bit, I suspect this might be a temporary situation. So I erased the code and reset the CEL. But if you end up doing what I’m doing, you need to know that the emissions test (at least in Texas) won’t pass you unless the car’s OBD-II has had time to complete a full cycle of the emissions tests. This will set a “has run” flag in the computer.
So if you’re planning to get your vehicle inspected after you erase the OBD-II’s memory (even if it wasn’t an emissions code you erased), you’ll have to drive the vehicle a bit before you can take it in for the test.
If you’re lucky (like me), your reader will have a handy red-yellow-green light system to tell you whether or not you’re ready for emissions testing. But if not, just remember to check for the “has run” flag — and absence of any emissions-related codes — before you go in.
Of course, if you don’t have a reader, you’ll have to just take off work, take your car in, and hope they don’t take your $40, walk back out 30 minutes later, and tell you that you’ll have to do the same thing again tomorrow or the next day because the computer’s not ready. Or worse yet, they tell you that you failed because of a random CEL. Doh!