Resetting the Check Engine Light for Inspection

My CEL went back on yesterday afternoon, 345 miles after having reset it, and about 100 miles after passing inspection. Here in NJ, we only need to get inspected every 2 years. :slight_smile:

I’ll probably look into it some more, as it’s worth having things operating properly, especially as in modern cars the components are interrelated - the computer adjusts things based on signals that it’s getting. But I can do this at my leisure.

What’s your take on these connectors that hook up the car to a laptop and read all sorts of other measurements (coolant temperature, O2 sensor data etc.) in addition to the code? I can see why a mechanic who does a lot of these doesn’t want to be bothered dragging laptops around the shop, but ISTM that these are a better deal for the casual DIYer.

But of course, that’s only if they work. I myself bought one of these ELM327 clones off eBay for under $20 earlier this week (it hasn’t come yet, as it’s being shipped from China so I can’t tell what it does).

I never really worked on cars in any serious way into the OBD-II era, so perhaps things are different now, but my impression is that they’re not significantly more useful for diagnostics than a regular code reader. Since car makers try pretty hard to make it so any odd sensor ranges that would cause problems will trigger a trouble code, problems that are diagnosable with raw sensor readings but which won’t trigger a trouble code are fairly rare.

They are pretty interesting and for a DIY-er or general car enthusiast they’re probably valuable as an education tool, so for instance if you know what the normal behavior of a sensor is, you might be more able to comprehend the implications of a trouble code saying that sensor is out of range. If the $20 one works, it’s probably worth that just for the neat-o factor!

I have one and it works well. You do get some more stuff compared to the simple readers. For instance, I can watch sensor readings in real-time. If I suspect a coolant temp sensor that is not setting a code (yet), I can start the car and watch the sensor readings as it warms up.

I can also watch the block learn at different rpms which tells me there is probably a small vacuum leak (again, not enough to set a code, but is still causing rough running).

It has other features I haven’t used yet, like it can make a graph of the O2 sensor voltage transitions which apparently will tell you that a O2 sensor is getting weak although it hasn’t failed yet.

I also like that it works on just about any car, it does a bunch of different protocols. The cheapos often only work on a few brands.