Hey Veeky Forumstto mechanics, I have ask a quick question: when 'exactly' does the CEL come on
Say I have a CEL >I just reset the computer by disconnecting the battery and it's gone (for now) >now the sensors are gathering info again >I drive about 200km and no CEL yet
I'm wondering if: 1. the CEL comes on immediately as a sensor detects something faulty or 2. if it comes only after all the sensors have completed its checks
(useless tidbit) I'm taking my car in for an emission test and I've got evap code and o2 sensor prob. I'm just hoping that I can pass by no tripping the two
If it's a consistent problem say running lean or rich it'll reappear after a set period of several startups T. Gs300 with lean code once a week
Carson Kelly
Going by that, I'm guessing it's #1 then (as soon as it detects any probs)?
Logan James
Different codes have different tolerances for when the light is triggered. Like x number of drive cycles.
Camden Morris
It depends on what it is, if it's constant like lean and such it'll be like said, the ECU is probably aware of the problem but it'll give it time assuming it might go away before throwing the code.
Jace Brown
Basically it will come on whenever the ECU detects a problem it can't fix by itself. Most of the time it's a dirty/bad sensor, shitty gas, etc. If it's a serious problem the car will start running poorly or switch into "limp home" mode. Most chain parts stores will loan you an OBDII scanner and look up codes for you. It won't tell you exactly what's wrong, but it'll narrow down the issue to a few options.
Ian Collins
Yeah, I dun have an obd2 scanner and my local shops don't lend them. I do know for certain it's an o2 sensor and evap (had a friend a while back with his scanner do a check). However...
After coming close to 300k now with no light, would you say I'm in the clear for that e-test?
Lucas Long
Clear it just before heading into emissions so it doesn't come up during it.
Cooper Phillips
Not entirely related but what obd2 scanner would you guys recommend? Looking at the bluedriver on amazon.
Aiden Powell
Yes buy that one.
Christian Russell
>paying a hundred dollars for a code reader when chinkshit 20 dollar units do the same thing
Tyler Robinson
Having used both the cheap ones are just awful, if you're not prepared to pay for good tools then why are you even in to cars?
Asher Mitchell
>Clear it just before heading into emissions so it doesn't come up during it.
this won't work, as it will give a "yellow light" because the car hasn't run enough cycles to clear the code. He'll be given a conditional pass and told to come back in a week or w/e
Adrian Thompson
What? My car clears codes if you leave the battery disconnected for a good 5 minutes.
James Taylor
It will work though. Cause that's exactly what I did to pass emissions. After I passed the light came back on when pulling out of the emissions place though, so I was cutting it close
Brandon Phillips
it clears the code but the scanner will give a "yellow" status ie there are still sensors that are checking the status before they give a green light ie "pass"
well that's not how it works if leafland where they do e-tests. Because if that were the case everyone with a CEL related to emissions would just disconnect their batteries before the test
Nathaniel Kelly
Buy this one its got amazing reviews ( I own one) works great, easy to use and costs 35 and its suppose to be a known brand. Dont buy those phone obd they can bend the plugs inside your cars obd and you will have to get that fixed.
its autel autolink al319 if you are afraid of clinking on link.
When the battery is disconnected or code is cleared the car goes in temp analyze mode and when you go to smog they will connect the scanner and if it goes yellow they will tell you to come back in a week and to drive the car for that time. Also depends on where you live some might just do a visual inspection or even let you pass if smog is within parameters even if you have a check engine light.
Luke Barnes
>1. the CEL comes on immediately as a sensor detects something faulty or >2. if it comes only after all the sensors have completed its checks Its both
Justin Wood
Depends entirely on what the fault is, user.
If it's an o2 sensor, then it takes time for the car to warm up and detect that there's a fault.
If it's something like a TPS or an evap leak, it might detect it as soon as you start the car, bringing the engine light back on immediately.
William Howard
each and every code has a different set of conditions for when it trips the CEL. Some are immediate and some take quite a few instances.
as for your EVAP problem, you will fail the emissions test even without the CEL coming on because the emissions test is an entirely different item in the OBD scan. it can tell if a sensor fails you immediately.
