So you’ve performed a code erase on your OBD-II-equipped vehicle, and now you’re due for an emissions check. But your code reader shows you’re not ready because some of the OBD-II emissions-related tests haven’t completed yet — specifically that the “HAS RUN” flag remains unset. What to do?
Well, you can drive around on your expired inspection sticker for a few weeks, checking until the flag goes away. But there’s a better solution: perform the manufacturer’s recommended drive cycle.
The drive cycle is a series of actions which, when performed correctly, will offer an opportunity for all the OBD-II tests to complete, leaving you with a fresh, ready-for-emissions-check computer. Cycles vary among manufacturers, but most take an hour or two to complete.
If you own the factory repair manual for your vehicle, you can find the correct cycle there. Or you can find them online. The folks who manufacture and sell the AutoTap OBD-II Diagnostic Scanner maintain a page that includes the GM and Ford cycles along with some helpful notations as to which part of the cycle activates which tests (link below). And if neither of these sources works for you, you can always resort to Googling “[insert manufacturer here] OBD-II drive cycle” for decent results. (As an optional variant, try adding the actual model to your search terms. That’ll help include model-specific forums, which often contain information of this type.)
For those of you interested, it looks like the personal issue with my trusty F150 involves the cat and evaporative emissions tests.
So it seems I need to drive a bit more. The EVAP section seems simple, though I’ll need to put some gas in to assure I’m between 15% and 85%. Sadly, my reader doesn’t allow me to directly monitor the FLI and EVAPOC sensors, so I’ll just have to hope. The second part seems a bit more tricky. Wish me luck!
(Thanks, mroach, for the great CC-licensed photo.)
The OBD-II Homepage [AutoTap]