# Resetting the Check Engine Light for Inspection **URL:** \ **Category:** Factual Questions\ **Created:** [August 31, 2010, 4:26pm UTC](https://boards.straightdope.com/t/resetting-the-check-engine-light-for-inspection/552156 "2010-08-31T16:26:48Z")\ **Posts on this page:** 3\ **Page:** 2
**Author:** ![Fotheringay-Phipps](https://avatars.discourse-cdn.com/v4/letter/f/d9b06d/32.png) [@Fotheringay-Phipps](https://boards.straightdope.com/u/Fotheringay-Phipps)\ **Post date:** [September 3, 2010, 1:29pm UTC](https://boards.straightdope.com/t/resetting-the-check-engine-light-for-inspection/552156/21 "2010-09-03T13:29:48Z")
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. 🙂 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. > [@GreasyJack](#): > > But you can get a cheap OBD-II code reader for under 50 bucks that will read and reset the codes. 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). ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [September 4, 2010, 12:00am UTC](https://boards.straightdope.com/t/resetting-the-check-engine-light-for-inspection/552156/22 "2010-09-04T00:00:29Z")
> [@Fotheringay-Phipps](#): > > 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. 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! ---
**Author:** ![zwede](https://avatars.discourse-cdn.com/v4/letter/z/ac91a4/32.png) [@zwede](https://boards.straightdope.com/u/zwede)\ **Post date:** [September 4, 2010, 8:38pm UTC](https://boards.straightdope.com/t/resetting-the-check-engine-light-for-inspection/552156/23 "2010-09-04T20:38:17Z")
> [@Fotheringay-Phipps](#): > > 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 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. [Previous page](https://boards.straightdope.com/t/resetting-the-check-engine-light-for-inspection/552156.md?page=1)