Anyone know how long after the Check Engine light has gone off a diagnostic can be run to determine why it went on? I've heard it has to be done immediatly for the computer to say why it is on, but wanted to know if anyone could confirm the time frame.

 

In terms of severity of the problem, if the CEL comes on for a while, then goes off, it is probably a minor issue that has cleared, such as a loose gas cap. If it comes on and stays on and driveability is not affected, you can continue the drive the car but should get it checked. If it comes on and stays on but driveability is affected (i.e., runs rough) you should get it checked as soon as possible. If it comes on and flashes on-off-on-off, you should shut off the car and have it towed to a service center or dealer (you can be hurting an engine component such as the catalytic converter).

As far as getting it read goes, some auto parts stores such as AutoZone will read the codes for free, as long as the CEL is still on. If it goes back out, they probably can't pull the information, although a dealer can.

 

Have the same situation on friday afternoon. No mechanics avalaible till monday morning. CHECK ENGINE LIGHT (CEL) was on. First from time to time, then constantly. Some problems when trying to accelerate, but not constantly. On monday constant problems with random loosing power. At the mechanich they have found trouble in a minute. Electric cable to spark number one was incoreect causing random missfire. As the guarantee (3 years) is still valid, price for replacement was zero.
If threre is no replacement cable in the moment, it can be of some help to clean carbon tracks on plastic and rubber part of cable which are causing this missfire, but replacement is recomended.
I ask how to reset CEL in "do it yourself" scenario; the answer was: unplug minus (-) power cord from battery for approx 1 minute (I have tried this - it works). It resets also clock and mileage counter (not the big sum but only the small one) and also average fuel consumption reading.

 

my check engine light has been on for 3 yrs just recently has been running bad, will start when I spray quick start into air duct,and after starts no problem until engine cools down maybe fuel filter i was told,any suggestions,also check engine lite is now off but running rough