I was just reading about different obd-2 scanners. My "SES" light has been comeing on a lot. I've been takeing it to the dealer to have a diagnostic test done. Anyways they say that my misfire is because of a bad #7 wire. I replaced the wire and the car ran great. Then all of a sudden the car started to run like crap again and the "SES" light came back on. When i was looking at the scan tools it had the option to "clear engine codes". So i was wondering do i have to get something to clear my engine codes? If i didn't clear the codes would they just come back on and make the car run bad again? Don't you got to fix the problem to make the codes go away. Somebody please help i'm a little confused about it all. All i know is this damn "SES" light is pissing me off.

 

anybody?

 

Pull the PCM BATT fuse for about 15 seconds. That will reset the pcm and clear most codes. If you have problems, the SES (and codes) will return. Your car may idle and act a little funny until some operational info is relearned.

 

So if i fix the problem the code won't come back right even if i don't pull the PCM BATT fuse.

 

as long as you fixed that problem your right the ses light will not come back on, but if you have more problems it will come back on, BTW bring your car to autozone , they will scan your car for codes free and tell you what parts you need if any, and they can clear your codes to after there done

 

See thats what i don't understand why do you got to clear the codes. Won't they just go away after you fix the problem?

 

you dont have to clear them, if the problem is fixed, the ses light wont come back on, but since your there getting it scanned why not clear the codes, thats what i did

 

So say for instance my SES light is on. I get it scanned. I get the codes. Then i have them cleared. If i didn't fix the problem at the same time wouldn't the codes come right back? If so whats the point of clearing them.

 

Most codes are held in "history" in the pcm's memory. Depending on the code, it takes x amount of driving cycles to erase it from memory. Sometimes the x amount is very high.

One purpose of clearing the codes is so they don't trip you up later when you have another (different) problem. This way, you won't see any code(s) but the current one(s) and will troubleshoot correctly.

If you clear the codes and do not fix the problem, the codes will come right back. If you clear the codes and it does not come back, that means that it was intermittent and the pcm is no longer detecting a problem.

 

I think you are confusing "active" codes with "stored" codes. When a problem occurs, it sets a code and stores it in the PCM. If will often, BUT NOT ALWAYS, turn on the SES light - not all the codes turn on the SES light. The PCM takes whatever corrective action is necessary, sometimes going to alternate sensors, programmed actions, etc. It stays in this condition until the problem is fixed, or goes away by itself. When the problem is gone and the code is no longer "active", the PCM reverts to its "normal" operating mode.

But, the code is stored, and remains in the PCM history, so that you can find out what turned on the SES light, even if the problem cured itself and the SES light went away. Or, if you had codes at some point that didn't turn on the SES light. It will remain stored until the engine completes a pre-determined number of "drive cycles" without the problem happening again. Then the PCM clears the code.

The "clear code" option is provided on scan tools so that the technician can fix the problem, then clear the code to make sure the problem is gone. Remember, not all codes turn on the SES light, so the only way to know if the code is present is to look at the PCM with a scanner, and the only way to know whether the code is "active" or "stored" is to clear it and see if it comes back.

 

oh okay, now i understand. Thanks for clearing that up for me. I was confused with the two like you said.