# Check Engine Light - I think it's just a gas cap. **URL:** \ **Category:** In My Humble Opinion\ **Created:** [October 28, 2009, 3:16pm UTC](https://boards.straightdope.com/t/check-engine-light-i-think-its-just-a-gas-cap/515448 "2009-10-28T15:16:55Z")\ **Posts on this page:** 2\ **Page:** 2
**Author:** ![Cowgirl\_Jules](https://avatars.discourse-cdn.com/v4/letter/c/4af34b/32.png) [@Cowgirl\_Jules](https://boards.straightdope.com/u/Cowgirl_Jules)\ **Post date:** [October 28, 2009, 9:36pm UTC](https://boards.straightdope.com/t/check-engine-light-i-think-its-just-a-gas-cap/515448/21 "2009-10-28T21:36:37Z")
> [@Joey\_P](#): > > Is your truck pre 1995? The only truck I’ve seen that did that didn’t have OBDII. It did have a harness for a reader though. I had to jump to or 4 pins in the harness then turn it on and off like 6 or 7 times and it would spit out the code via the CEL. No, I can do it in either my 2004 or my 2005. Bearflag, I was browsing the Costco flier at lunch, and they have a code reader at [costco.com](http://costco.com) for about $35, that seems to give you a little more than just the code. Don’t you just know I can’t find it online. If you want, I’ll look in the flier again when I get home. ---
**Author:** ![JFLuvly](https://avatars.discourse-cdn.com/v4/letter/j/ac91a4/32.png) [@JFLuvly](https://boards.straightdope.com/u/JFLuvly)\ **Post date:** [October 28, 2009, 9:44pm UTC](https://boards.straightdope.com/t/check-engine-light-i-think-its-just-a-gas-cap/515448/22 "2009-10-28T21:44:34Z")
OBD11 (On Board Diagnostics) came out in 95 or 96 I think. The problem with the cheap readers is that alot of times they just flash LEDs and you have to count the flashes. This can be a pain in the buttt with multiple faults. Also, I don’t think they are capable of resetting a fault only telling you where the problem is. An EVAP fault is pretty common and I think also deals with the gas cap. [Previous page](https://boards.straightdope.com/t/check-engine-light-i-think-its-just-a-gas-cap/515448.md?page=1)