The Check Engine Light Explained

Check Engine / Service Engine Soon / SES light

Todays vehicles use many sensor, switches, solenoids, and other electrical components to control or monitor every aspect of the engine. From controlling the fuel and ignition systems, to monitoring the emissions. A problem in any of these systems, or subsystems, can cause the check engine light to come on.

The first step in any diagnosis of the check engine light is to get the computer (PCM or ECM) scanned for codes. Any time this warning comes on, a code is stored in the computer memory along with many data parameters that were present at the time of the fault.

A simple code reader that can be purchased at any automotive supplier can retrieve these codes. Many of the large national parts store chains will scan the system at no charge. The code will give an indication as to what system has / had a problem. The more expensive scanners will also show live data, and allow further diagnosis by being able to control parts of a particular system.




Service Engine Soon and Traction Off lights are steadily on.
 ANSWER: Many codes that turn on the check engine light, will also tun on the Traction warning. Need to have the engine computer (PCM) scanned-repaired first.

My Check Engine Light on my 1997 Check Engine Light will come on after ignition is shut off.
 The computer (PCM or ECM) is what controls the check engine light. You may have a bad computer or a shorted wire.

Yes, I have the same issue on my 1996 Lesabre. Check Engine Lite and Traction Off... The car runs bad in town, but nice on the highway at 70 and above. Once warmed up it is allot better... Any recommendation?
 It could be any numbers of problems. Spark plugs, plug wire, ignition coil, fuel injector etc. The fist step is to have the computer scanned for codes.

i got code p0455 were is the problem?
 P0455 is for a large EVAP system leak. Either the gas cap is loose, not sealing, a line is leaking or you may have a vent or purge solenoid problem.

i have a vehicle light with a wrench in middle want to know what this means.
 Sounds like you are describing the "Service Vehicle" light. Either needs an oil change and get it reset, or a problem in an body system component and needs the Body controller scanned.

I get regular oil changes and tune ups so the other day when my check engine light began flashing I didn't know what to think was wrong. It drives but when the car sits idle it feels as if it wants to shut off (It doesn't) it shakes just a little until i catch speed. I went to an auto parts store where he hooked it to a machine that read Cylinder 1 but then he sold me an ignition coil, spark plugs and wires???? I pray a simple coil replacement and tune up repair this problem. My friend had the same issue with his Lexus truck and that regimen worked for him. I pray it works for me as well.
 The shaking you feel at idle is a cylinder that is misfiring. Usually it is ignition related, so a coil or new wires and plugs will most likely take care of it. It can at times be a fuel injector problem, so if your ignition repairs don't fix the problem, you should look into that.

i have an 01 Oldsmobile Alero that will not stay charged (battery) alternator good had checked check engine light on. Any ideas
 This problem is called a parasitic draw. Something is staying powered on when the car is off and key is removed. You would need an amp meter and schematics to repair this. Removing fuses one at a time until draw goes away is a good start.

Need help I have a 2005 Silverado on the dashboard have a light that reads a lock light what can I do it doesn't want to start.
 This is the security warning light. the truck is in theft mode, that is why it won't start. You may have a bad ignition cylinder housing or ignition switch, of a faulty aftermarket remote start / alarm system if your truck has one.

I have a 1999 S-10 Pickup truck, Jan 09 it totalled stalled out with the Service Engine Light on spark plug wires, dist cap, rotor were all replaced, a year later water pump, hose assembly pump replaced, light still coming on and off at random, July 11 had all spark plug wires replaced dist cap, rotor etc replaced all this for $1500 and the dang light still pops on, truck runs with a little hesitation right before the light comes on and then it will just go out for no reason, doing nothing to make it go out, last suggestion was a new gas cap??? Any help would be great.
 Your engine has a misfire. You need to get the codes scanned in the computer to even guess what may be wrong. One thing is for sure, it is NOT the gas cap!

Code readers of any kind will not get the codes to flash. Even the manual jumper to get the codes to flash doesn't work. 94 S-10 V6 Vortec, new body style. In general the truck runs fine, but it bothers me that I can't read the codes. What is keeping the codes from being read?
 If you cannot get the codes in any way, then you may either have a communication circuit problem between the computer and the diagnostic connector or a bad PCM. If it is a bad PCM, then it is just the a problem in that part of the computer, and will not cause any problems with the way your truck runs.

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